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of medieval jewel work (such as that in the South Kensington Museum) reliquaries, covers for the gospels, etc., made either in Constantinople from the 6th to the 12th centuries, or in monasteries in Europe, in which Byzantine goldsmiths' work was studied and imitated. These objects, besides being enriched with precious stones, polished, but not cut into facets, and with enamel, are often decorated with filigree. Large surfaces of gold are sometimes covered with scrolls of filigree soldered on; and corner pieces of the borders of book covers, or the panels of reliquaries, are not unfrequently made up of complicated pieces of plaited work alternating with spaces encrusted with enamel. Byzantine filigree work occasionally has small stones set amongst the curves or knots. Examples of such decoration can be seen in the South Kensington and British Museums.

In the north of Europe the Saxons, Britons, and Celts were from an early period skilful in several kinds of goldsmiths' work. As early as the middle of the 5th century the brooches and other personal ornaments of the "Littus Saxonicum" in England were encrusted with enamel, often set in bands of pure gold, and the enamel work varied with borders or centres of filigree.

The Irish filigree work is more thoughtful in design and more varied in pattern than that of any period or country that could be named. It reached its highest perfection, according to Dr. Petrie, in the 10th and 11th centuries. The Royal Irish Academy in Dublin contains a number of reliquaries and personal jewels, of which filigree is the general and most remarkable ornament. The "Tara" | brooch has been copied and imitated, and the shape and decoration of it are well known. Instead of fine curls or volutes of gold thread, the Irish filigree is varied by numerous designs in which one thread can be traced through curious knots and complications, which, disposed over large surfaces, balance one another, but always with special varieties and arrangements difficult to trace with the eye. The long thread appears and disappears without breach of continuity, the two ends generally worked into the head and the tail of a serpent or a monster. The reliquary containing the "Bell of St. Patrick" is covered with knotted work in many varieties. A two-handled chalice, called the "Ardagh cup," found near Limerick a few years since, has belts, bosses at the junctions of the handles, and the whole lining of the foot ornamented with work of this kind of extraordinary fineness. The late Lord Dunraven (Royal Irish Academy Trans., vol. xxiv.) numbers forty varieties of pattern on this cup alone. Some are the Greek fret with Celtic varieties, spiral trumpet-shaped lines, interlaced bands, knots, and arabesques, all in several varieties. Much of the medieval jewel work all over Europe down to the 15th century, on reliquaries, crosses, croziers, and other ecclesiastical goldsmiths' work, is set off with bosses and borders of filigree. Filigree work in silver was practised by the Moors of Spain during the Middle Ages with great skill, and was introduced by them and established all over the Peninsula, where silver filigree jewelry of delicate and artistic design is still made in considerable quantities. The manufacture spread over the Balearic Islands, and among the populations that border the Mediterranean. It is still made all over Italy, and in Albania, the Ionian Islands, and many other parts of Greece. That of the Greeks is sometimes on a large scale, with several thicknesses of wires alternating with larger and smaller bosses and beads, sometimes set with turquoises, etc., and mounted on convex plates, making rich ornamental headpieces, belts, and breast ornaments. Filigree silver buttons of wire work and small bosses are worn by the peasants in most of the countries that produce this kind of jewelry. Silver filigree brooches and buttons are also made in Denmark, Norway, and Sweden. Little chains and pendants are added to much of this northern work. Beautiful specimens have been contributed to the various international exhibitions.

Some very curious filigree work was brought from Abyssinia after the capture of Magdala-arm guards, slippers, cups, etc., some of which are now in the South Kensington Museum. They are made of thin plates of silver, over which the wire work is soldered. The filigree is subdivided by narrow borders of simple pattern, and the intervening spaces are made up of many patterns, some with grains set at intervals.

Great interest has been felt in the revival of the designs of antique jewelry by Signor Castellani. He collected

examples of the peasant jewelry still made in many provinces of Italy on traditionary designs preserved from a remote antiquity. Most of the decoration is in filigree of many varieties. It was in part through the help of workmen in remote villages, who retained the use of vari ous kinds of solders, long forgotten elsewhere, that the fine reproductions of antique gold filigree have been so beantifully carried into execution in Italy, and by Italian jewellers in London.

For examples of antique work the student should examine the jewel room of the British Museum, the Campana collection in the Louvre in Paris, and the collection in the South Kensington Museum. The last contains a large and very varied assortment of modern Italian, Spanish, Greek, and other jewelry made for the peasants of various countries. The Celtic work is well represented in the Royal Irish Academy in Dublin. (J. H. P.)

FILIPPINO. See LIPPI.

FILLAN, ST. The accounts given by various writers of this saint, in so far as they supply any details, are, as in many similar cases, purely legendary and conjectural. That such an ecclesiastic existed, that he was of Irish origin, and that he was venerated in Glendochart and Strathfillan in Perthshire as early as the 8th or 9th century, may be held as certain. There was an ancient monastery in that district dedicated to St. Fillan, which, like most of the religious houses of early times, was afterwards secularized. The lay-abbot, who was its superior in the reign of William the Lion, held high rank in the Scottish kingdom. This monastery was restored in the reign of Robert Bruce, and became a cell of the abbey of canons-regular at Inchaffray. The new foundation received a grant from King Robert, in gratitude for the aid which he was supposed to have obtained from a relic of the saint on the eve of the great victory of Bannockburn. Another relic was the saint's staff or crozier, which became known as the coygerach or quigrich, and was long in the possession of a family of the name of Jore or Dewar, who were its hereditary guardians. They certainly had it in their custody in the year 1428, and their right was formally recognized by King James III. in 1487. The head of the crozier, which is of silver-gilt with a smaller crozier of bronze inclosed within it, is now deposited in the National Museum of the Society of Antiquaries of Scotland. It was secured for them through the exertions of Dr. Daniel Wilson, author of the Prehistoric Annals of Scotland. This crozier has attracted much attention among Scottish antiquaries, and its history has been minutely investigated.

On the subject of this article reference may be made to Cosmo Innes's Sketches of Early Scottish History, pp. 389–394, 623– 624; Bishop Forbes's Kalendars of Scottish Saints, pp. 341–346; and specially to the Historical Notices of St. Fillan's Crozier, by the late eminent antiquary Dr. John Stuart, who died while this, his latest work, was passing through the press.

FILLMORE, MILLARD (1800-1874), thirteenth president of the United States of America. His family was of English stock, and had early settled in New England. His father, Nathaniel Fillmore, made in 1795 a clearing within the limits of what is now the town of Summer Hill, Cayuga co., New York, and there the future president was born, January 7, 1800. The father went by the title of "the squire," and served as a justice in the beginnings of the settlements nearest to him, which were very sparsely occupied. Millard, to the age of fourteen, could have shared only the simplest rudiments of education, chiefly from his parents, with slight help from a school. At that age he was ap prenticed, for the usual term, to a fuller and clothier, to card wool, and to dye and dress the cloth from the farmer houses. Two years before the close of his term, he, by a promissory note for thirty dollars, bought the remainder of his time from his master, and entered a retired lawyer's office as a student and helper at the age of nineteen. He, of course, received and accepted the usual honor extended to young men of his proclivities, to deliver the Fourth of July Oration, before he was twenty-one years of age. In 1820 he made his way to Buffalo,-then only the germ of the present flourishing city, and supported himself as a student in another law office by teaching a school and aiding the postmaster. In 1823 he was admitted an attor ney in the court of common pleas, Erie co., and then took up legal practice at Aurora, to which his father had removed. Hard study, temperance, and integrity gave him a good reputation and moderate success, and he was made

an attorney and counsellor of the supreme court of the State. In 1826 he married Abigail, daughter of the Rev. Lemuel Powers. Returning to Buffalo in 1830 he formed a partnership with two lawyers, both afterwards distinguished in public life, and became successful at the bar. From 1828 to 1831 he served as a representative in the State legislature, coming in as an anti-mason. In the single term of 1832-4 he was a representative of his district in the national Congress, as anti-Jackson, or in opposition to the administration. From 1836 to 1842, when he declined further service, he represented his district as a member of the Whig party. In Congress he opposed the annexation of Texas as slave territory, was a warm advocate of internal improvements and a protective tariff, supported J. Q. Adams in maintaining the right of offering anti-slavery petitions, advocated the prohibition by Congress of the slave trade between the States, and favored the exclusion of slavery from the District of Columbia. His speech and tone, however, were moderate on these exciting subjects, and he claimed the right to stand free of pledges, and to adjust his opinions and his course by the development of circumstances. The Whigs having the ascendency in Congress during the latter part of his membership, he was made chairman of the House Committee of Ways and Means. Against a strong opposition he carried an appropriation of 30,000 dollars for Morse's telegraph, and secured important provisions in the new tariff measures of 1842. He found some supporters of his proposed nomination as a candidate for vice-president in the Whig National Convention at Baltimore. In May, 1844, being the Whig candidate for the governorship of New York, he was defeated by Silas Wright. In 1847 he was made comptroller of the State of New York, an office of manifold responsibilities and duties, which he resigned on his election, in November, 1848, as vice-president of the United States, Zachary Taylor being president. He presided over the senate ably and impartially during the seven months of exciting debate and agitation on the so-called "Compromise Measures," and Mr. Clay's "Omnibus Bill," which, though finally defeated as a whole, substantially succeeded in its general bearing on several matters of intense import to the nation as connected with the subject of slavery.

President Taylor died July 9, 1850, and the next day Fillmore, according to the special provision of the constitution, took the oath and acceded to the highest office, being hen fifty-one years old. The cabinet which he called round him contained many distinguished men, as Webster, Corwin, Crittenden, Graham, Hall, and Kennedy. On the death of Webster in 1852, Edward Everett succeeded him as secretary of state. The president sent a force to protect New Mexico in the dispute as to its boundaries with Texas. The critical matter which gave its historic significance to his administration was that chief one of the class of "compromise" measures, the enactment of the Fugitive Slave Law, to make effective a provision of the constitution for the rendition of "fugitives from labor or service." Being instructed by Crittenden, his attorney-general, that the bill was not inconsistent with the constitutional sanction of the Habeas Corpus, the president signed the bill, and issued a proclamation calling upon Government officials to enforce it. These measures roused the most passionate opposition and animosity, among Whigs as well as anti-slavery men. The attempt to enforce the odious law was resisted by mobs in various free States, and was made, for the most part, wholly ineffectual, the people being resolved to regard it as annulled by the "higher law." The fact that the president had signed and sought to enforce the law, though he might plead for himself constitutional obligation, and a purpose of patriotic fidelity in the exercise of his best judgment, made a breach between him and his party. But few questioned the sincerity and purity of his intentions, or his own full persuasion that the measures were of vital necessity to pacify the nation. Still, as the result was a sharp and embittered variance among his previous supporters, his administration was regarded as inglorious, if not as a failure. In many other matters of high public concern, his official course, as indicated by his appointments, the recommendations in his messages, and the projects which he devised, was characterized by sound discretion, by humane promptings, and practical wisdom. His advice, however, even on these matters, was not always followed by Congress. That body having approved a plan for the extension of the Capitol, the president, on July 4, 1851, laid the corner

VOL. IX.-384

stone of the new edifice, Daniel Webster being the orator of the occasion. In the same year he interposed promptly and effectively in thwarting the projects of the "filibusters," under Lopez, for the invasion of Cuba. Commodore Perry's expedition to Japan, that of Lieutenant Lynch to Africa, and that of Ringgold to the Chinese Seas, with the exploration of the valley of the Amazon by Herndon and Gibbon, may be referred to as engaging the executive ability and wide forethought of the president. His term closed March 4, 1853. In the preceding autumn he had been an unsuccessful candidate for nomination for the presidency by the Whig National Convention, and he yielded his place to Franklin Pierce. Three weeks before the close of his term his wife died in Washington, and he quietly returned, with a son and a daughter, to private life in Buffalo. In 1854, he travelled extensively through the southern and western States, and in 1855-6 he visited Europe, moving from place to place in a quiet and unostentatious way, but receiving much courteous attention. He declined the proffered honor of D.C.L. from Oxford. While in Rome he was informed of his nomination for the presidency by the "Native American" party, the nominees of the other parties being Buchanan and Fremont. In 1858 he married Mrs. Caroline M'Intosh of Albany, a lady of fortune and culture. Retiring to his home in Buffalo, he enjoyed a studious retirement among his books and friends, taking no public share in political affairs. He took great interest in the Buffalo Historical Society, of which he was the president. His life closed March 8, 1874, in his seventy-fifth year. All who knew him in any relation accorded in regarding hin as an upright and conscientious man, blameless, loving simple ways, and heartily devoted to the best interests of his country. (G. E. E.)

FILM. See CAPILLARY ACTION and OPTICS. FILMER, SIR ROBERT, a writer of the 17th century, remarkable for his singular political theory, which deserves notice on account of the great attention which it excited, was the son of Sir Edward Filmer of East Sutton in Kent. He studied at Trinity College, Cambridge, where he matriculated in 1604. His death has been fixed at widely different dates, but of these the most probable is 1653. Filmer was already a middle-aged man when the great controversy between the king and the Commons roused him into literary activity. His writings afford an exceedingly curious example of the doctrines held by the most extreme section of the Divine Right party. Filmer's theory is founded upon the statement that the government of a family by the father is the true original and model of all government. In the beginning of the world God gave authority to Adam, who had complete control over his descendants, even as to life and death. From Adam this authority was inherited by Noah; and Filmer quotes as not unlikely the tradition that Noah sailed up the Mediterranean and allotted the three continents of the Old World to the rule of his three sons. From Shem, Ham, and Japheth the patriarchs inherited the absolute power which they exercised over their families and servants; and from the patriarchs all kings and governors (whether a single monarch or a governing assembly) derive their authority, which is therefore absolute, and founded upon divine right. The difficulty that a man "by the secret will of God may unjustly" attain to power which he has not inherited appeared to Filmer in no way to alter the nature of the power so obtained, for "there is, and always shall be continued to the end of the world, a natural right of a supreme father over every maltitude." The king is perfectly free from all human control. He cannot be bound by the acts of his predecessors, for which he is not responsible; nor by his own, for "impossible it is in nature that a man should give a law unto himself"-a law must be imposed by another than the person bound by it. With regard to the English constitution, he asserted, in his Freeholder's Grand Inquest touching our Sovereign Lord, the King and his Parliament (1648), that the Lords only give counsel to the king, the Commons only "perform and consent to the ordinances of parliament," and the king alone is the maker of laws, which proceed purely from his will. It is monstrous that the people should judge or depose their king, for they would then be judges in their own cause. The most complete expression of Filmer's opinions is given in the Patriarcha, which was published in 1680, many years after his death. His position, however, was sufficiently indicated by the works which he published during his

lifetime:-the Anarchy of a Limited and Mixed Monarchy (1646), an attack upon a treatise on monarchy by Nicholas Hutton, which maintained that the king's prerogative is not superior to the authority of the houses of parliament; the pamphlet entitled The Power of Kings, and in particular of the King of England (1648); and his Observations upon Mr. Hobbes's Leviathan, Mr. Milton against Salmasius, and H. Grotius De Jure Belli et Pacis, concerning the Originall of Government (1652). Filmer's theory, owing to the circumstances of the time, obtained a recognition which it is now difficult to understand. Nine years after the publication of the Patriarcha, at the time of the Revolution which banished the Stuarts from the throne, Locke singled out Filmer as the most remarkable of the advocates of Divine Right, and thought it worth while to attack him expressly in the first part of the Treatise on Government, going into all his arguments seriatim, and especially pointing out that even if the first steps of his argument be granted, the rights of the eldest born have been so often set aside that modern kings can claim no such inheritance of authority as he asserted.

FILTER, an arrangement for the separation of impurities from liquids, by passage through porous material. The filtering process is common in nature. The clearness of spring water is due to it; for such water generally comes from a considerable depth in the ground (as appears, e.g., from its equable temperature throughout the year); and having traversed a variety of porous strata, it has undergone a straining action, producing the beautiful transparency we observe. This does not, of course, represent absolute purity, for the liquid retains in solution various substances acquired by contact with the strata through which it has percolated. The operation of filtration is extensively practised in purification of water, on a large scale for supply of towns and cities (now an important branch of civil engineering), and on a small scale for domestic purposes, and for the use of ships on a long voyage, etc. It is also a valued method in chemistry and

the arts.

The mechanical action of straining, by which all particles larger than the interstices of the porous material are arrested, is one important function of filters, and it used to be commonly represented as their only function. They may act, however, in other ways to purify water. Not to speak of the further mechanical actions of subsidence on upper surfaces of particles of the filtering medium, and lateral attraction and adhesion of suspended matter (which doubtless occur in some measure), it is an important fact, now well ascertained, that a filter may separate from water a portion of the matter held in solution. On the other hand, it is often precisely such matter, when of organic origin and putrescent (and minute invisible disease-germs may here be included with the matter in solution), that it is specially desirable to remove from drinking water as being prolific of mischief when taken into the system. In numerous instances an outbreak of virulent disease, such as typhoid fever, has been clearly traced to water so contaminated. The danger is the greater that such water may be bright and sparkling, and peculiarly palatable.

That even sand has the power of removing dissolved matter from water was shown by Mr. Witt's valuable experiments at Chelsea, described in 1856. In one of these, e.g., water containing 1:42 grains of chloride of sodium per gallon (70,000 grains) was deprived of 22 per cent. of that substance by filtration through a depth of 1 foot 9 inches of sand. The sand had no appreciable action on dissolved organic matter, as charcoal had, but the quantity of such matter originally present was small. It is probable that all finely porous material has such action, more or less. The efficiency of charcoal in this respect, and especially fresh animal charcoal, has been well demonstrated and utilized. The mode of the disappearance of dissolved organic impurities has been a disputed point. Some say they are retained and accumulated in the pores of the charcoal; but the experimental evidence seems to leave little doubt that they are mainly oxidized, so as hardly to impair the activity of the filter. In fact, the value of a filtering material will be found to depend chiefly on the power it has of bringing oxygen, stored in its fine pores or otherwise provided, into chemical union with the dissolved organic matter and destroying it. At the same time it is obvious that, chiefly by the mechanical action of straining, organic matter may accumulate in a filtering medium, and in course of time,

through decomposition, render the water which passes through more impure and less wholesome than in its unfiltered state.

We may remark here that river water and shallow well water, while extensively used for water supply, are in general the most largely polluted. Rivers commonly receive large volumes of sewage, impure surface water from cultivated land, and other contamination. The water of shallow wells, especially in large towns, or when near churchyards, stables, cesspools, etc., is often contaminated with organic matter of the worst kind, in large quantity. While rain water, collected from the roofs of houses in butts, no doubt contains organic matter, this hardly bears comparison in amount to the organic impurity in rivers (thus Dr. Hassall found it a hundredfold less). Deep spring water, again, is freed from much of its organic impurity through natural filtration. The advantages of a good lakesupply for large towns has been amply demonstrated in these days, notably in the case of Glasgow, which draws its water from Loch Katrine.

Though the arrangements for water supply of most of our large towns include filtering processes by means of which, as a rule, excellent drinking water is abundantly provided, so that in the opinion of some chemists a domestic filter may be superfluous, while it is sometimes a source of harm (owing to lack of proper attention), it is generally thought a wise additional safeguard to employ one of those instruments, in view, more especially, of some of the possible consequences of epidemics and floods, and the necessity of house-storage of the water received. In country places, and in various other circumstances, their use is often quite imperative if the laws of health are to be respected. The Japanese and Egyptians seem to have used water filters at an early period. These consisted of sandstone or unglazed earthenware, and were of bowl or egg shape, with small projections at the top resting on a wooden frame. The water poured into this vessel filtered through to a vessel below. About the middle of last century, slabs of a lias found in Picardy were used as a filtering agent, being fitted as a false bottom in water cisterns; the water was drawn off through a tap from the space below. A porous filtering stone of Teneriffe was at one time imported largely into England. The "alcarrhazas" are filter vessels of porous biscuit stoneware made in Spain. One of the earliest filters in England was that patented by Mrs. Johanna Hempel in 1790. It was a supported basin made of tobacco pipe (or similar) clay and coarse sea, river, drift, or pit sand, and hardened in the furnace. In the following year (1791) the ascending principle was first applied by Mr. James Peacock. Water from an upper reservoir was admitted through a pipe to the bottom of a box containing strata of sand, gravel, and a mixture of charcoal and powdered calcareous stone. Passing_up through this, it was drawn off by a pipe at the top. The filter was occasionally cleaned with an exhausting and condensing pump, which sucked up water rapidly through the filtering material and then sent it back with force, washing out the dirt.

The construction of filters is a matter on which inventiveness has been largely exercised. All sorts of porous substances have been called into requisition, as may be seen by a glance at the patent records. Thus, to mention some of these, we have various kinds of stone, sand, gravel, pow dered glass, clay, porous sulphur, preparations of iron, charcoal (vegetable and animal), cloth, felt, horsehair, skins, paper, silicated carbon, sponge, wood, wool, cane, capillary threads, and so on. Vegetable charcoal, we may note, was first employed in 1802, animal charcoal in 1818, and solid carbon blocks in 1834.

It is impossible here, and it would be tedious, to give anything like a detailed account of the changes that have been rung on the filtering principle for domestic filters. In the simplest and most familiar forms, of course, the water passes down by its own gravitation through the filtering medium to a reservoir below. The force of downward pressure has sometimes been augmented by a head of water, sometimes by a force pump, and sometimes by means of air condensed above the water to be passed through the filter. Or the air has been extracted from the vessel containing the filtered liquid, thus adding force to the atmospheric presure above. The ascending princi ple has appeared in various applications; and in some cases the water has been caused first to descend and then to &

cend through filtering material (a vertical partition, e.g., being fixed in a vessel so as to reach nearly to the bottom, and layers of sand and vitrified limestone being placed on either side of the lower part; the water is poured in on one side of the partition and drawn from the other side near the top). Lateral filtration has also been tried. Filters have been arranged to act in the cistern, or in connection with the service pipe between the cistern and the water tap, or independently, and, in the latter case, either having the unfiltered water poured into them, or being placed in a vessel of it, and giving filtered water through a tube. Sometimes a series of separate connected vessels have been employed; and for very dirty water it is often advantageous to have one system of filtration for the coarser, and another for the finer impurities. Once more, filters have been rendered self-supplying by means of a ball-cock. These are some of the general forms which the filter has taken.

The application of pressure to filters cannot as a rule be pursued very far, for it tends to derange the apparatus and render the filtered liquid muddy. Enlargement of surface is a better means of obtaining rapid filtration. Upward filtration, while it offers some advantages over downward, has not hitherto come very much into use. It is open to objection in that the water sent upwards has a tendency to force a passage through certain channels, without being uniformly disseminated in the material; and the deposit of any filth is excluded from view, and mostly also from smell, instead of being exposed and giving us warning.

In passing now to examine more closely some of the approved forms of domestic filter at present in use, it should be borne in mind that while any of these filters will doubtless purify water both mechanically and chemically, more or less, it is only on condition of their being properly attended to, and the filtering material renovated at intervals depending on its nature and the nature and amount of impurity in the water. The term "self-cleansing," applied to some filters, may have a (limited) true sense, but if understood to imply that a filter, let alone, will go on ad infinitum giving pure water, it is quite inapplicable; solid impurities must accumulate and call for removal. The statement, occasionally made, that a filter is "warranted to remove all impurities" from water is absurd and hardly deserves notice. Absolutely pure water is a thing almost unknown; careful distillation alone will give an approximation to it. Again, the claim that a filter will remove all lime from water is often false; filtration is capable of removing only a small quantity of lime. It must be allowed that sundry points in the process of filtration still remain in some obscurity, and it is matter of regret that the action of some common filtering agents has not been so fully cleared up by scientific experiment as others. Still enough has been ascertained probably to guide to the construction of a filter on rational principles.

In a large proportion of filters, as already indicated, some form or other of carbon is the chief filtering agent. The well-known filters of Lipscombe are cylindrical-shaped covered vessels of glazed earthenware, in which the filtering medium, a mixture of vegetable and animal charcoal, in granular form, is enclosed between two slabs cemented in the case. The upper (glazed earthenware) slab has a central aperture with raised border, and a small perforated basin immediately below it; into this is inserted a sponge to arrest the grosser impurities, which is taken out and cleaned at short intervals. The filtered water passes through the lower (and porous) slab to the reservoir below, which communicates above with the outer air by a narrow tube passing up within to the top of the apparatus, and delivers its water through a tap.

FIG. 1.-Decanter Filter.

Charcoal in the form of solid finely porous blocks, which can be conveniently brushed and cleaned externally, is

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now often moulded for filters. The convenient decanter filter in which the water passes through the block to a central tube, forms an elegant addition to the sideboard. The annexed figure (1) represents one of these as made by Atkins, who also furnishes earthenware filter vessels having a division across the inside wherein a carbon block is fitted water-tight, which can readily be taken out and cleaned and replaced, or a fresh one substituted. Sometimes the block is fitted in a movable pan. Again, in the filter shown in fig. 2 a double filtration is effected, the water passing first through loose charcoal B, then through a charcoal block C, supported as shown. The block in this case is said to last longer without cleaning. The movable and perforated earthenware plate A, which is placed above the charcoal (see fig. 3), allows of easy renewal of the latter. The charcoal used in these filters is chiefly of vegetable origin. They are found to remove more or less of organic and inorganic matter dissolved in water.

It may be useful here to call attention to some of the conclusions arrived at regarding charcoal in the sixth report of the Royal Commission on Rivers' Pollution a short time ago. Fresh animal charcoal has been proved to act powerfully in the removal of organic impurity (considerably more so than vegetable charcoal), as well as of mineral matter. But, according to Dr. Frankland, its reduction of the hardness ceases in about a fortnight, the removal of organic matter continuing even after six months, though to a much less extent, especially if the filter be much used. It was found necessary to renew the charcoal every six months when used for filtering the comparatively pure FIG. 2.-Filter with double water of the London New action. River Company, whilst the water of the Thames required renewal of the charcoal every three months. If this be not done, myriads of minute worms, we are told, are developed

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FIG. 3.-Plate at A in figure 2.

in the material passing out with the filtered water. Other statements of scientific weight, regarding animal charcoal are more favorable to it, and to show that under certain conditions, perhaps imperfectly understood, it may give better results.

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In Major Crease's system, which is adopted in the British army and navy, loose animal charcoal is compressed between plates by means of a screw, the amount of compression being de termined by the degree of impurity

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in the water to be filtered.

The silicated carbon of Mr. Dahlke's filters is obtained by mixing animal or vegetable charcoal with the residue of

distillation of Boghead coal. By adding a little clay to the latter product, and saturating the whole with oily matter, it can be moulded, after which it is burnt. In one form of the filter, two carbon blocks are sealed into the interior of an earthenware vessel, granulated carbon being placed between them; in another, a double action is obtained by placing a carbon block over the entrance to a second carbon medium. These filters have been highly commended for their chemical properties, attributed to magnetic oxide of iron present in the medium. We give (fig. 4) a representation of the silicated carbon siphon filter with its case. Water may be sucked through it from a stream directly into the mouth, or passed siphon-wise from

FIG. 4.-Silicated Carbon Siphon Filter.

One vessel into another. These and similar pocket filters | roasting hematite iron-ore with granulated charcoal for of Atkins's were supplied to the Ashantee expedition.

A very powerful filtering medium was discovered and

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twelve to sixteen hours at a dull red heat. Mr. Spencer considers the purifying property of the oxide to be due to its power of attracting oxygen to its surface, without the latter being acted upon, the oxygen attracted being then changed into ozone, by which the organic matter of the water is consumed. The magnetic carbide is used in granular form. This filter gained prize medals at the last London and Paris exhibitions, and its efficiency was demonstrated by the Lancet Sanitary Commissioners' report on filters in 1867.

The only other system we shall here notice is that in which spongy iron is used. This substance is metallic iron which has been reduced from an oxide without fusion. It is in a spongy or porous state of extremely fine division. Its remarkable purifying action on water was discovered by Professor Gustav Bischof of the Andersonian University, Glasgow; and experiments made with his filters by the Royal Commissioners already referred to showed that their power both of removing organic matter and reducing the hardness of water even increased during upwards of eight months' constant use. The general form of the filter is represented in fig. 5. An inner vessel containing the spongy iron is supported in a case, which, below, contains some prepared sand, a regulator A, and a receptacle C, for filtered water (with tap, not shown). The unfiltered water B is in this form supplied from a bottle which is inverted into the upper part of the inner vessel (a method familiar to chemists). After passing through the spongy iron, the water ascends through an overflow pipe in the direction of the arrows; the object of this is to keep the spongy iron, when once wet, constantly under water, as otherwise it is too rapidly oxidized. The object of the prepared sand (which is generally in three layers, viz., pyrolusite at the top, then sand, then gravel) is to separate traces of iron retained in solution. The regulator A consists of a tin tube cemented in the position shown; it is open at the inner end, which is below the perforated bottom supporting the sand, and closed by a screw cap at its outer end. It has also a small lateral perforation, through which alone the filtered water passes into the reservoir. Should the perforations get choked, the screw cap is removed, and a brush inserted; on starting at first, too, the cap is unscrewed, that the materials may be well washed out without soiling the lower reservoir. With a ball-cock and constant supply of water, the inner vessel is dispensed with.

The nature of the action of the metal on organic matter is rather obscure. Mr. Bischof considers there are both reducing and oxidizing agencies constantly at work, and that the oxides of iron, being present in their nascent state,

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