who had slept the preceding night in barns and sheds, and 4325 males and 3700 females whose sleeping-places were caravans and tents, or under the open canopy of heaven. The numThe boundaries of these municipal boroughs bers living out of houses vary with the seasons. In winter they shrink into such dwellings as

are available to them, and in summer they swarm out into the lanes, commons, and fields. The ascertained houseless class amounted to 20,348 persons in 1841, in 1851 to 15,764, in 1861 to 11,444, and in 1871 to 10,383. The census in 1841 was taken in June; on the three subsequent occasions it was taken in March and April. The class appears, therefore, to be undergoing a gradual reduction.

to which the vessels were lying. These vessels include 96 of her Majesty's ships, with 13,454 persons on board; 9193 British seagoing vessels, with 40,188 persons; and 1437 foreign and colonial vessels, with 12,545 persons on board.

There were also 10,976 persons enumerated in barges and boats on inland waters, as com. pared with 11,915 persons so enumerated in 1861, and 12,562 in 1851.--(Digest of English Census. JAMES LEWIS. London, 1873.)

Maritime Population.-66,187 persons were enumerated on board 10,726 sea-going vessels European Statistics.-The following tables, lying in harbours, creeks, and rivers, in the extracted from the Registrar-General's report last census, and have been included with the for 1871, show the population of the more population of the several parishes contiguous, important European countries:— ITALY (inclusive of VENETIA).-POPULATION, NUMBERS, and PROPORTIONS per 1000 of MARRIAGES, BIRTHS, and DEATHS, in the Years 1863 to 1871.

* The decrease of marriages in 1866 may be attributed to the law which then came into operation, rem97, ing the civil registration from the parochial authorities to the communes; there had been a marked increase in the previous year, resulting from a wish to evade the law about to come into operation. Doubtless many of the marriages solemnised in the churches during 1866 escaped registration.

†The figures of 1870 were supplied by Signor L. Bodio, chief of the Statistical Department in Italy.

SPAIN. POPULATION, NUMBERS, and PROPORTIONS per 1000 of MARRIAGES, BIRTHS, and DEATHS in the Eleven Years 1861 to 1871.

NOTE.-The population enumerated at the census of 1860 was 15,673,536. The estimated population f the years subsequent to 1861 has been deduced from the excess of births over deaths in each year f method of estimating the population is sanctioned by the Junta General de Estadistica at Madri decline of registered marriages in 1870 is believed to be due to the introduction of civil registration, whil occurred during that year.

Porridge-See OATS, &c.
Porter-See ALCOHOLIC BEVERAGES, BEER,
HOPS, MALT, &c.

Port Sanitary Authority—Ports.-The Local Government Board may by provisional order permanently constitute any local authority whose district or part of whose district forms part of or abuts on any part of a port in England, or the waters of such port, or any conservators, commissioners, or other persons having authority in or over such port or any part thereof (which local authority, conservators, commissioners, or other persons are in the Public Health Act referred to as a "riparian authority"), the port sanitary authority of the whole of such port or of any part thereof.

members of all or any of the riparian authorities having jurisdiction within such ports, or any part thereof.

The Local Government Board may, if it thinks fit, temporarily constitute by order any such authority, until a provisional order for its permanent constitution is confirmed by Parliament, and may from time to time renew any such last-mentioned order, and may by any such order make any such provisions as it is empowered to make by provisional order.

Any order constituting a port sanitary authority may assign to such authority any powers, rights, duties, capacities, liabilities, and obligathe mode in which the expenses of such authotions under the Public Health Act, and direct rity are to be paid; and where such order constitutes a joint board the port sanitary authority, it may contain regulations with respect to any matters for which regulations may be made by a provisional order forming a united district under the said Act.-(P. H., s. 287.)

The order of the Local Government Board constituting a port sanitary authority gives jurisdiction over all waters within the limits of such port, and also over the whole or such portions of the district of any riparian authority specified in the order.-(P. H., s. 288.)

A port sanitary authority may, with the sanction of the Local Government Board, delegate the exercise of their powers to any riparian authority within or bordering on their district.-(P. H., s. 289.)

The mayor, aldermen, and commons of the city of London are the port sanitary authority of the port of London.-(P. H., s. 291.) For the provisions with regard to the expenses of port sanitary authorities, see EXPENSES.

A great many port sanitary authorities have now been constituted in England, but sufficient time has not yet elapsed to pronounce any judgment as to the amount or the efficiency of the work done. The whole of the Irish coast has also been divided into districts, and placed under the control of port nuisance authorities.-(Second Annual Report of Local Government Board for Ireland, 1873-74.)

A very serious responsibility rests upon every port in the kingdom. Each vessel

The Local Government Board may also by provisional order permanently constitute a port sanitary authority for the whole or any part of a port, by combining any two or more riparian authorities having jurisdiction within such port, or any part thereof, and may pre-arriving from abroad requires to be most scribe the mode of their joint action; or by forming a joint board consisting of representative members of any two or more riparian authorities, in the same manner as is by the said Act provided with respect to the formation of a united district.

The Local Government Board may also by provisional order permanently constitute a port sanitary authority for any two or more ports, by forming a joint board consisting of

narrowly examined, for the history of the past shows that cholera and other diseases have again and again been imported; and from want of effective regulations, persons actually and evidently labouring under disease have been allowed to land and infect a whole nation. The duty of every medical officer of health connected with a port is to insist upon a proper hospital being erected or adapted, as the case may be, so that on the arrival of an

infected vessel the sick may immediately be isolated. In large ports he should be provided with a sufficient staff to enable a thorough inspection of every vessel coming to our shores to be efficiently carried out, and he should therefore have a small steamer or other means of locomotion at his disposal. It well admits of argument whether the appointment of medical officers of health to ports ought not to be taken out of the hands of local authorities, as the importation of cholera is a national calamity, and therefore the necessary precaution should not be left to the unequal and sometimes unintelligent action of local authorities.

Port Wine-See WINE.

Post-Mortem Examinations-Any local authority may provide and maintain a proper place (otherwise than at a workhouse or at a mortuary) for the reception of dead bodies, for the purpose of undergoing authorised post-mortem examinations.-(P. H., s. 143.) See MORTUARY.

Potassium (K-391)-A metallic element discovered by Sir H. Davy in 1807. Specific gravity, 865; fusing-point, 144.5° F. (62-5 C.) This remarkable substance is a bluish-white metal, which at the common temperature of the air is so soft that it can easily be cut by a knife, but at 32° F. it is crystalline and brittle. It has a most powerful affinity for oxygen, rapidly tarnishing in air, and decomposing water, with the production of flame, when thrown upon it.

water may be detected by the loss of weight the salt suffers when heated; the silica, by adding to it hydrochloric acid in excesS, evaporating to dryness, and igniting the residuum by which the contamination is rendered insoluble. The sulphates and chlorides may be detected by adding nitric acid in excess, and testing the liquid with nitrate of silver and chloride of barium. If the former produces a white precipitate, a chloride is present; and if the latter does the same, the contamination is a sulphate.

Potassium, Chromate of (K.CrO1), prepared from chrome ore, a natural octahedral chromate of iron found in various parts of Europe and America, and the bichromate of potassium (K.Cr.O), prepared from the above, have been extolled by Dr. Angus Smith as being powerful antiseptics, but their price is too great to allow of their being largely employed.

Potassium, Cyanide of (KCN or KCy), is a highly poisonous salt, extensively used in photography and gilding. Accidents from its employment are not uncommon. It has a local chemical action upon the skin, and if this be abraded or wounded, it may be absorbed, and produce serious effects. The symptoms produced by the salt are the same as those produced by prussic acid-2} grains being equal to 50 drops of medicinal prussic acid. It has been found as an impurity in reduced iron. It may be detected by the tests previously given for potassium, and it gives a white precipitate with nitrate of silver, which, when dried and heated, possesses all the properties of cyanide of silver. If a solution of proto-sulphate of iron is added to a solution of the cyanide of potassium, and after agita tion the mixture is treated with diluted sulphuric acid, Prussian blue will be produced.

The salts of potassium are very numerous. They are all soluble in water, and most of them are colourless. They may be recognised in a pure state by the violet hue they impart to the blowpipe flame when heated in platinum wire, by giving no precipitate either with sulPotassium, Nitrate of.-Saltpetre (KN0]). phuretted hydrogen or with sulphide of am-Specific gravity, 1925 to 1975. monium, and by giving a yellow crystalline precipitate with bichloride of platinum, and a white crystalline precipitate with tartaric acid, when the latter is added in excess to moderately strong neutral or alkaline solutions. We can only here notice a few of the salts of potassium.

Potassium, Arseniate of (KH,AsO4), is prepared with arsenious acid and nitrate of potash. It forms large crystals, which are soluble-in about 4 parts of water, and insoluble in alcohol. It is employed medicinally, and also to form a resist paste in calico-printing and in the manufacture of cobalt blue. See ARSENIC.

Potassium, Carbonate of (K,CO), often contains an undue quantity of water, as well as silicic acid, sulphates, and chlorides. The

The salt occurs as an efflorescence on the soil in the East Indies and elsewhere; it is also produced artificially on the Continent ty exposing nitrogenous matters mixed with a calcareous earth to the atmosphere. A nitrate of calcium is slowly formed, lixiviated out and decomposed by wood ashes, the main result being that carbonate of lime is precipitated, and nitrate of potash remains it solution, from which it is recovered by evaporation and crystallisation.

Nitrate of potash is a dimorphous salt, its usual form being that of six-sided strated prisms, but also occurring in microscopic rhom bohedra. It is soluble in about three and a half times its weight of cold water, and a third of its weight of boiling water; it is insoluble in alcohol. It fuses without decomposition