The conclusions arrived at by Dr. Joule are the following:

1st. That under the new system, great accumulations of deposit would take place, which, being carried into the river by storm overflow, would continue to pollute the Thames.

2nd. That the sewage would not be entirely prevented from returning to the metropolis.

3rd. That the river would be rendered particularly noxious at the point where so vast a quantity of offensive matter was to be concentrated; and, in consequence, the large float population, as well as the inhabitants of Greenwich, Woolwich, Gravesend, &c., would suffer most severely.

4th. That the air confined in the new mains would seriously increase the already enormous volume of putrid gases in the sewers.

5th. That the system, as well as that which it was to supplement, could not be considered otherwise than very filthy; inasmuch as, instead of removing sewage to the soil, which is a natural deodoriser, it would cause its accumulation in the bed of the river, at only a few miles distance.

In dwelling upon those points of agricultural economy, the neglect of which must soon impoverish our internal resources, and lead to national distress, the author showed that the daily waste occasioned by the wholesale loss of the constituents of organic growth is, in London alone, equivalent to 2,723 tons of butchers' meat, potatoes, and bread, and 860,000 gallons of milk, beer, and other liquid food-a loss which would speedily reduce the country to a state of barrenness, were it not for the importation of large quantities of food and manure from foreign counproduce of the Chincha Islands, which afford it tries. But guano cannot last for ever. If the most abundantly, and of the best quality, was reserved for the sole use of Britain, they would, at the present rate of consumption, be exhausted in sixty years. The author also pointed out that with regard to the importation of cattle, corn, and bone manure, such supplies would continue only so long as foreign governments remained ignorant of the permanent injury inflicted on their own fields. Liebig has already complained that, if the exportation of bones continued at the present rate, the German soil would become gradually exhausted.

There can be no doubt that the soil of nearly the whole of Europe is becoming gradually exhausted; nor is the future, when sterility must meet the increase of humanity, so far distant as to be beyond the limits of our anxious consideration. Sterility is no necessary consequence of the increase of consumption, as is proved by the agricultural history of Holland and of China. But when the traveller from these countries, and from "New Zealand, shall take his stand on a broken pier of London Bridge," and look upon the limpid Thames, no longer bearing to the sea the rich freight of ammonia and phosphates which should give strength and life to failing crops, he may, perhaps, moralize upon the strange fatuity which, in an age of science, could give nature's materials of life to infusoria and fishes. When these latter have been devoured by sea-birds, and the ammonia and phosphates deposited on ocean rocks,

England may no longer require guano!

We heartily concur with Dr. Jonle in asserting that we should not be satisfied with merely keeping our agriculture from decline, but that, with a rapidly-increasing population, the wisest course would be to reserve such supplies of guano as we may be able to obtain for the purpose for which it would seem to be designed by nature-that of forming a fertile soil where sterility at present exists. To effect this, we must cease to regard rivers as the "natural drainage of cities!" But it appears hopeless, in the present condition of suicidal neglect of the all-important principles of

agricultural chemistry, to look forward to their adoption as a measure of policy and commonsense by the administrative wisdom of this country. DESMOND G. FITZGERALD.

27 Upper Berkeley-street, Portman-square.

| but there may be circumstances attendant on the abrading action of a shot in an oblique direction, such as the one-sided resistance it meets with, which might, in most cases, cause it to rebound, before that resistance could be equalised on all sides by sufficient penetration; and this would depend on those practical circumstances just mentioned, the effect of which experiment alone could IRON-COATED SHIPS. determine. Now, the perforation by shot is, I GENTLEMEN,-In the very excellent paper by apprehend, the great thing to be dreaded, and it Mr. E. J. Reed, one of the editors of the ME- is possible they may be turned aside by the CHANICS' MAGAZINE, recently read at the Society obliquity of their action under the conditions speof Arts, upon the changes which, during the pre- cified, although without that expedient they may sent century, the ships of the Royal Navy have not. If, however, the author means by "crushing undergone a paper abounding in information force" not that which is exerted in the penetraand judicious observations-there is one statetion of the plates, but that which is the result of ment to which I may be permitted to allude as the blow, in the rending or crippling of the timnot being, I think, fully developed. bers to which they are the casing, then these obIn some remarks on the proposal to place theservations are altogether in aid of his argument. diminish correspondingly the thickness of the "iron armour" of ships at an inclination, and to plates, so as to lessen the load, it is observed, that "it needs no appeal to experiment to show that the proposed arrangement would not be attended by any advantage, for the simplest theoretical consideration shows that, for a given height of bulwark, the same quantity of metal will be required to resist a given blow, whatever the inclination may be," inasmuch as the diminished thickness would be exactly compensated by the additional extent of casing. You are well aware that caution and suspicion are entertained by me, almost to the amount of a crotchet, in respect to the truthfulness of the conclusions of mere science in their applications to practical matters, there being so much that is abstract, so much that requires modification by empirical means, before we can arrive at truth in its concrete practical reality Can experiment be dispensed with in the present instance ? I think not.

If a

"If a shot moving horizontally strikes an inplate is equal to the crushing force which would clined plane, the crushing force exerted upon the have been exerted upon it if upright, multiplied by the sine of the angle between the inclined plate and the horizontal.". Now this is true only of an abstract, non-abrading, non-crushing blow, upon an abstract, unimpressionable surface. shot exerts "a crushing force," it is retarded, is wholly unaffected by the sine of the angle at more or less; and if entirely, the crushing force which it strikes, for it is wholly spent. It is true, no doubt, of momentum, as imparted to a body in a direction perpendicular to the inclination of its surface, but only in the abstract again, perfectly elastic bodies. In a breaching force, upon the assumption of the collision being between both the direction and the amount of the components, in its alleged resolution, is altered, if not ignored altogether, and both the cause and its effects require to come under another measure besides that of momentum. A blow, to be viewed prac tically, must be seen in two aspects, as the result of, and measurable by, momentum, and what more especially belongs to practice, as the result of, and measurable by, vis viva; and it is in the latter aspect that crushing effects must be contemplated. The species and phenomena of force cannot be limited to what is observable of momentum alone; and it will depend on practical circumstances, such as the comparative hardness of the conflicting materials, on the velocity being the prominent factor in the vis viva of the shot, and on the particular angle at which it strikes, whether it shall freely glance from, crushingly graze, or more crushingly lodge in, or penetrate through, the iron casing of a ship; and the only investigation of these actions and their causes is the experimental.

Well, all this tends only to strengthen the position which the author of the paper has taken, "that the side of a ship will require the same weight of metal upon it, in order to resist horizontal shot, whether it be upright or inclined," inasmuch as the expedient of inclination being nullified in the case of a free glancing shot, it would be yet more useless, in case the shot should hang and tend to penetrate. This is true so far,

The great enemy which these tortoise ships of war will have to contend with, is the rifled cannon with steel shot-that is, if bursting can be prevented-for here the velocity of the projectile is prodigiously increased, and it is according to the square of the velocity that its destructive effects must be estimated. Hence, a pretty close proximity will always be necessary in an attack on these tortoises, and an armament with a long range will constitute at once their security, and their dangerous character as a foe.

I am, Gentlemen, yours, &c.,
BENJ. CHEVERTON.

PENETRATION BY ELONGATED RIFLED IRON SHOT AND SHELL. GENTLEMEN,—In the highly instructive and valuable paper read by Mr. Reed, at the Society of Arts, on the evening of Wednesday last, he makes the following observation:-"It is a deiron plating can yet be made available. By ap fence against shells and hollow-charged projectiles generally, and against those only, that plying iron of very great thickness between wind and water, we may reduce the liability to injury by shot to that important part; and it may be well to do this; but if the upper works are made shell-proof, we can export no more. These considerations reduce the question to a form in which it may be practically dealt with, and I doubt not the solution is not very distant."

As I was invited by a letter of invitation from the Secretary, by order of the Council, to take a part in the discussion, I wished to say that, from that period, in presence of several members of the experiments I made at Cork, nearly seven years ago, with the two-groove 14-bore service rifle of council of the National Exhibition held there; and from the results of those experiments I felt confident that rifled cannon would sooner or later be adopted in the service; and the wonderful range and accuracy of fire obtained by Mr. Arm

strong's rifled cannon fully bore me out in my exthe mind of the Chairman, I was not allowed to pectations. But as, from some misconception in proceed, I now beg to state that, judging by the results of those experiments, no iron armour can against elongated iron shot and shell, formed be put on a man-of-war that will be a protection after the manner of those I experimented with at Cork, although iron armour would be a protection Beamish's letter to the editor of The United against Paixhan's shells. An extract from Col. Service Journal, of August, 1852, fully and clearly explains the nature and results of those

experiments.

I am, Gentlemen, yours, &c., Rosherville, 20th Dec. J. NORTON.

FINE ARTS.-We understand Mr. Greville Fennell has been experimenting on hard and soft vulcanite, in order to make it subservient to th uses of the artist, as a medium for receiving i! colours. We hope shortly to publish an accoun of all his experiments. Mr. Fennell intends liberally to present the result of his labour to the profession.

SUFFIELD'S IMPROVED SHIPS' PUMPS. We have had numerous improvements in ships' pumps lately, for which we ought unquestionably to be grateful. No disaster can be more appalling than the sinking of an inhabited ship at sea, unless it be the burning of such a ship, and it is to the pumps that we have, of course, to trust, in the event of accident, for security from both these evils. The extent to which the ocean now swarms with passenger ships renders us eager to embrace every real improvement in these appliances, however modest and unpretending its character may be. For this reason we bring an im. proved pump, arranged and manufactured by Messrs. Suffield and Co., of Bermondsey-wall, to the notice of our readers. This pump has no very remarkable novelties embodied in it. Its great merit lies in its careful adaptation, by a person of great practical experience, to the varied requirements of service on board ship. For many purposes, where the duty is not too severe, Mr. Suffield fits his pumps with Perreaux's valves, which are now becoming well known, and specimens of which may be seen in operation at the South Kensington Museum. nessed the working of the Suffield pump, fitted with these valves, and found the results truly astonishing: The great and most characteristic merit pump is the liability it has to cheke.

The advantage of the Perreaux valve in this respect is well understood; and, on the occasion just referred to, we saw bulky pieces of sacking, workmen's jackets, and other like articles, drawn completely through the pump, without any evil effect whatever, and without any kind of difficulty.

In the annexed engravings we have represented, in fig. 1, a side elevation partly in section and in fig. 2, a front view one-half in section, of one of Mr. Suffield's pumps, fitted with Perreaux's valves, and arranged for working with cranks, flywheels, and common handles. The channels, AA, are formed separate from the barrels, BB, in which the plungers, CC, work. The passages, AA, from the suction-pipes, DD, to the barrels, BB, are fitted with valves, EE, opening inwards towards the barrels. aa are castings or feathers, and bb wedges for keeping the valves in their places. The delivery from the barrels takes place through ports, HH, fitted with other valves, E'E', opening outwards into a common pipe, fitted with a dome or air vessel, Q, and with two screwed collars, I and J. For pumping purposes, the delivery takes place through the upper collar, I. We recently wit-under-collar, J, is closed by a screw-cap, and the On the contrary, when the pump is to be used as a fire-engine, the upper collar I, is closed, and the hose is strewed on to the under collat

the upper part of the vessel forming an airchamber.

Although we have spoken of these pumps mainly as ships' pumps, they manifestly need but little modification to adapt them to various other purposes. When fitted on board ship, suctionpipes are led from various parts of the ship, and their upper ends are all brought together in a casting, close to the main suction-pipe leading to close them. Then, by means of a goose-neck, or the hold, and are all furnished with screw-caps to other suitable coupling-piece, the pump may be connected to either of the suction-pipes, and thus made to draw from any part of the ship.

At the trial of the improved pump referred to above, we were unable to institute any comparative tests with existing pumps; but the flow kept so copious and so uniform as to leave but little up by a few men from a depth of many feet was doubt of the efficient working of the machine. Indeed, it was the opinion of one very experienced engineer who was present, that he had never and we must acknowledge that his opinion was before seen results equal to those then obtained, not formed without considerable reason. demand for the improved pump-proceeding, as it does, from a well-known firm of great practical experience-is so great that several dozens are Perreaux valve where the duty is not too now in progress of manufacture. We have said that Mr. Suffield uses the severe. He does not, however, confine himself to the use of this valve, but prefers, in some cases, ether valves of an improved description.

The

has endeavoured to propound, and which will undoubtedly hereafter become an established formation in steam warfare." The English fleet was in two parallel lines-the windward one led by Nelson, in the Victory, and the other by Collingwood, in the Royal Sovereign. As these two lines advanced, at about a mile-and-a-half per hour, each of the foremost ships, the bows of which were square and thinly planked, was under the raking fire of the broadsides of eight or nine ships, consisting of hundreds of guns. Before the Victory could reply by a single gun, she had lost fifty men, and had her main top-mast, with all her studding sails and booms, shot away. After having been under fire forty minutes, she reached the enemy's line, and ran into the Redoutable just as her tiller-ropes were carried away by a shot from that ship. Admiral de la Gravière thinks that, with ordinary gunnery practice on the part of the French and Spaniards, Nelson would have seen his ships smashed to pieces by those of the French, like cavalry when improperly attempting to break the squares of steady infantry; and Sir Howard Douglas is of opinion that, "if the present improved state of gunnery had existed then, the divisions of the British fleet would have been entirely disabled before they came to close action." What is more manifest than that such actions as these

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were won by sheer 'pluck, in opposition to, and in contempt of, scientific strategy. Thus it has ever been. The Dutch, the French, and the Americans have done their naval work scientifically; and, although they have been so overmatched in the end that the foremost amongst them is compelled to say, "Je ne suis pas de ceux qui dans l'illusion de l'amour-propre nationale, nous croient en état de lutter sur mer d'égaux à égaux contre la puissance Britannique," yet they have made their selt-confident enemy suffer severely for his rashness. But, while Englishmen have been thus neglectful of naval strategic science, France has given birth to Paul l'Hoste, a man who may be said to have been its creator; and among her sons are still to be found some of its ablest expounders.

Hitherto the great difficulties in handling sailing ships, and the capricious nature of the elements on which success depended, have frequently deranged the most skilfully-devised plans of operation, and rendered anything like complexity uncertain and dangerous. Ships in order of battle have formed in lines ahead or in lines abreast, and there was but little else they could do with anything like precision.

"But steam propulsion entirely annuls all the limitations and disabilities imposed by the wind on the evolutions of fleets, and opens the whole surface of the ocean as a battlefield for the contests of steam flects. The movements of steam fleets may, like those of armies, be conducted on tactical principles best adapted to the great end of all preliminary mana uvres--the formation for battle in the most simple, speedy, and precise manner. This power of executing the evolutions of fleets and armies on the same tactical principles, cannot but be considered as one of the greatest benefits which will result from the application of steam propulsion in naval warfare. The intended formation may, in all cases, be accomplished by steam flects, with as much precision as the formation of an army on land, and with the like regard to the avoidance of a premature display of the whole force, or a disclosure of the intentions of the commander. . . . With this new power it may be presumed that success will more than ever depend upon the tactical skill and the quick perception of the chief, together with prompt and resolute execution on the part of hos under his command."

Naval officers of the old school," says our author, "may at first sight be disposed to repudiate, perhaps to ridicule, the adoption, in their profession, of the principles of military movements and formations, as recommended and expounded by the author. But, moved as fleets will hereafter be, by the obedient agency of steam, so that the station of each ship in a fleet, and the time to be occupied in performing any evolution, can be determined with as much exactness as the post of a regiment or brigade in an army, it must follow that the evolutions of ships of war will be susceptible of being executed with a precision hitherto unknown in the naval service. . . . The rude practice of forming a fleet for battle in one long line has hitherto prevailed in naval warfare, on account, chiefly, of the difficulties and uncertainties imposed by the wind, in executing compound evolutions with sailing ships. These difficulties will not exist for fleets consisting wholly of steam-ships. Armies in the field move in as many columns as there may be practicable roads or opened routes leading to the point at which

The Prince de Joinville, in his famous Note sur l'etat des Forces Navales de la Frunce,

the intended deployment in order of battle is to take place; but at sea a steam fleet may always be moved in as many columns as there are divisions in its formation, and each ship of a fleet may be considered as corresponding to a batalion in a land army."

If this be true, it is of the utmost importance that our naval officers should set themselves in earnest to the study of naval tactics, which we have the highest authority for saying they have not yet done. Sir Howard Douglas, in the work before us, shows carefully, clearly, and as fully as his limits permit, how the principal military manœuvres may be made available in naval

actions.

The former half of the book is taken up by a brief history of the introduction of steam as a moving power to ships, and "an account of the nature and action of steam machinery in its application to the paddle and the screw, together with an inquiry into the relative values of these agents with respect to their powers of communicating motion, and to their conveniencies in the armament of ships of war." Of this part we can say but little. The latter half-on naval tactics-forms an admirable supplement to Sir Howard's incomparable work on "Naval Gunnery." "If we might presume to offer advice to Sir Howard, we should say the sooner it is incorporated with that work the better. He need have no anxiety about the fate of the other portion, as it will, in our opinion, never do him any abiding credit. After this statement of our opinion, minute criticism is unnecessary. There are, however, two things in it we should like to notice. One has reference to the tremulous motion of the sterns of screw-ships, and the other to the use of the trunk in screw-ships of war. The author says, on the first point :"The shake of the screw, and the consequent injury to the stern of the ship, are caused by the sudden and violent reactions of the disturbed water in that place against the blades of the screw as they enter and emerge froin thence. The rectilinear edges of the ordinary screws are, in this respect, highly disadvantageous, since the whole of an edge enters and leaves at once the water on each side of the aperture; within which aperture the water is comparatively in a quiescent state; but if the leading edges of a screwblade were curved, as A' pB, Gp'H', in the figure, they

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would slide obliquely and continuously through the water, like a screw formed with an entire feather, so that at no moment would there be any shock or discontinuity of action." Page 60.*

We are afraid that Sir Howard's screw would do very little towards reducing the shock complained of; for the ordinary practice of using two small portions of a screw surface instead of an entire thread has two effects, against which he makes no provision, but which are undoubtedly the main causes of the shocks. The first is, that

Sir Howard says further that these curved edges would also have the advantage of readily throwing off any floating materials that may come in contact with them. He proposes, also, that the curved parts should be furnished with sharp edges, partly notched like saws, and made of a metal capable of resisting the corroding effects of sea water, by which means they would be rendered capable of dividing any rope, spar, or other floating matter, like a powerful circular saw.

when one blade of the screw comes vertically over the other, a body of water is driven against the after stern post, and is brought to rest by the resistance the post offers to it. The tremor of the stern has been, in fact, considerably diminished by fitting angular pieces of wood on the foremost face of this post, and is said to have been almost entirely removed in some cases by working the screw abaft the rudder. The other of these causes is, that a quantity of water is driven off sideways by the blades of the screw, as well as fore-and-aft-the upper blade driving it in one direction, the lower blade in the other. If these two forces were exactly balanced, the stern would not be moved towards either side. But they are not so balanced. The water driven off by the upper blade moves much more freely than that acted upon by the lower one. The upper blade is, in fact, not unfrequently partially out of the water. The consequence of this is, that at every semirevolution an unbalanced pressure is brought on the screw in the direction opposite to that in which the lower blade moves. This is equivalent to a series of blows on one side of the stern-post. Similar forces are also brought into action vertically in consequence of the difference between the resistance on the blade moving upwards, and that on the blade moving downwards. Were the screw complete, we should have continuous pressures in the directions named, instead of the more mischievous intermittent ones. But it will be seen at once that the alteration in form proposed by Sir Howard would not tend to diminish any of these forces.

Again, our author has conceived a violent dislike to the trunk or framework round the well through which the screw is raised. He says that it interferes with the armament of line-of-battle ships, where the free use of two guns on each deck is, on this account, greatly impeded: consequently, he says, there may be said to be only two stern-guns on each deck which are wholly effective. Now, we do not think that this objection is wellfounded. It is true that there are only two guns on each deck of our screw line-of-battle ships which can fire in the line of the keel, and therefore which are effective as stern-guns; but that this is not owing to the presence of the trunk may be seen from the fact that our sailing ships have no more. The statement that "by sup pressing the trunk, the stern-batteries on each deck would be strengthened by the two guns which the trunk had rendered useless," is without foundation.

He says, also:

"The steerage of the ship is greatly impeded by the intervention of the trunk, which renders it impossible to use a long tiller, and permits only the substitution of two short armis of a lever, called a yoke, which works within the small space between the trunk and the stern. . . . . The arms of the yoke being short compared with the length of an ordinary tiller, it has been found necessary, in order to obtain sufficient power to turn the rudder, to have a multiplying purchase consisting of a system of pulleys near the end of cach arm of the yoke, and also in a main beam in its rear. In consequence of the complexity of this apparatus, a considerable revolving motion of the steering-wheel is neeessary in order to produce even a small movement of the rudder; and there is therefore a want of promptitude in the corrective power of the helm, when moved by the yoke, which is not experienced when a ship is steered by a simple tiller in the ordinary way." And again," the great force which it is necessary to apply to the wheel in order to give motion to the rudder, particularly when the latter is acted upon by sudden and violent impulses from the striking of waves against it, is also the cause that the steering of screw steamers having trunks, is far less steady than that of ships whose helms are managed by the ordinary tiller."

Are not these statements self-contradictory? There is a certain work to be done by the man at the wheel-viz., to overcome the resistance of the water to the motion of the rudder through any nature of the machinery intervening between the given number of degrees. Now, whatever be the man and the rudder, he must-neglecting friction -perform exactly this amount of work. Representing, then, the work done at the rudder by a certain quantity, consisting of pounds multiplied by feet, he performs this quantity by moving a less number of pounds through a greater number of feet-the nature of the machinery regulating the relative numbers of pounds and feet. If by