beyond which the electro-metallurgic process would not be advantageous. As we proceed in size, the parts are large in themselves, and are moreover modelled in a massive style, to comport with that size, whereby the roughness of the surface, and the inexactitude of minor details, become matters of so little moment, that the ruder process of casting is amply sufficient. Indeed the literal transcript of every minutia of the surface which the electrotype gives, is a disadvantage even in the smallest works of art, unless the model be susceptible of, and has received, the highest finish. But in a large statue, the eye removed to the proper distance, regards only the general form.

I have heard it remarked that the marble statues of Sir Francis Chantrey never produced a finer effect than when seen by twilight in the workshop in a half-finished state; that is, just from the hands of the pointer. This is a severe but a true test of intrinsic worth, the judgment being unbiassed by meretricious or even adventitious excellence of mere execution, either to enhance the merits of the work, or to extenuate its faults. Now colossal statues are seen not only in an analogous point of view, but under conditions yet more restrictive and exacting. I allude to those of the first magnitude, and whose situation is of course in the open air; for those of a secondary size, if placed in buildings, and particularly if the material is marble, are not subjected to circumstances so inimical to effect. But the large colossals are placed generally on high-they are seen with advantage only at a distanceand the calculated intention of the style in which they are modelled is, that they should be both seen and appreciated only at a considerable distance. For this purpose, all the parts, and even the features, are massive and few in number. The modelling is in a style of grandeur to correspond with the grandeur of magnitude. The minuter details of likeness are omitted; those that remain are not delineated in literal conformity to the lifesize bust of the individual, but are exaggerated to such a degree, that if the artist took the direction of the ludicrous instead of the grand, it would amount to a caricature. So situated, they are exposed to a diffused light unfavourable to shade, and to the discrimination of

parts; and this evil is greatly aggravated by the dingy hue which, in our climate, at least, they very quickly assume, to the effect of swallowing up shadow in colour. If, in such circumstances, the form, as defined by the general contour, is inelegant or unbalanced, no superficial arrangement or division of parts, however bold in character, will suffice to redeem it; no cutting, however deep, which does not go to the extent of letting the light through, will obviate the bad effect it will have in the distance, although, perhaps, to the beholder, when in the artist's studio, the deep shades thus produced may be thought amply sufficient to afford the relief intended. In these colossals it is the outlines that tell effectively, and also the shadow which projection throws, far more than the shade which incutting affords.*

These observations lead me to the only case in which I can admit that iron would be a proper material for statues; for where artistic skill finds so little room for display-where it is confined to the highest quality of the art, and within limits of such severe simplicity-where the advenient means usually found so effective to pourtray composition and design, are rendered nugatory by being almost or altogether lost to view, it cannot, in an artistic point of view, be a matter of the slightest importance what the nature of the material is, what the character of its surface, or what indeed its colour, unless the statue can be prevented from becoming black. The microscopic accuracy of delineation afforded by the electrotype process will cease to have any utility long before it arrives at this extreme point, but here it is manifestly useless; even the coarseness of iron castings, the impossibility of fusing them together, the rude and joint-showing method of uniting them by inside flanges, and the inaccuracy of their fittings, are all matters of the utmost insignificance; and therefore iron, as being

The finest statue in the metropolis for colossal qualities, though hardly itself to be called colossal, is, in my judgment, that of Pitt, by Chantrey, in Hanover-square. Its syminetry and balance, from whatever side, or at whatever distance, it may be viewed, is-if I may be allowed something like an Hivernianism-perfect to a fault. Its outline in any direction is elegant, and pregnant with meaning and indication of what perhaps the spectator is too distant distinctly to perceive through the medium of light and shade. Its style, also, is eminently grand and dignified.

cheapest and strongest, and the least liable to excite the cupidity, or yield to the fanaticism, of future generations, is undoubtedly in this case the best material that could be employed. Next to this, in the descending order of size, and wholly grounded on considerations of taste, I would rank granite and marble, reserving ivory and bronze for the miniature productions of art; but as our climate is unfavourable to durability in exposed situations, matters of taste must occasionally be overruled by considerations of expediency, and therefore bronze is the best material for statues of a moderate size in the open air. The durability of cast iron is a subject on which I cannot here enter; but if properly protected from special chemical and galvanic influences, in respect both to the constitution of the metal, and to circumstances connected with the construction of a statue, it would surely last long enough to satisfy the most ardent cravings after monumental immortality; as long, at least, as the time when, to use the words of a prophet, "a solitary traveller from Australia shall be found sketching the ruins of the last arch of London bridge."

I cannot conclude without adverting with feelings of deep regret to the timidity which is exhibited by patrons of art, and other influential men of taste, in refraining to countenance any monumental design which departs in the least from what precedent has sanctioned, or goes farther, at most, than ringing changes on what it has dictated. Certainly, they are safe within the circle of plain stone columns, and respectable marble, bronze, or stone statues, from any very stinging condemnatory criticism; but if we are always to go on thus, we shall never ourselves be cited as precedents. Let us at least try what we can do in colossal granite statues, and having put forth our might to the extent of rivalry, at any rate, with the Egyptian, we may next take courage to go beyond him, and, with that spirit of enterprise and originality which has so honourably marked our onward career in all matters appertaining to public convenience and utility, break away from the leadingstrings by which art is trammelled, through a slavish deference to authority. Our Gothic forefathers, self-emancipated from Greek and Roman bondage, created, as well for posterity as for themselves,

an entire new style in architectural art; and that, too, at a time when scholastic prejudices in favour of the ancients were at the highest. If it be not Classic, let it then be British usage, to erect statues in cast iron, but of a size and character so colossal, that, far from militating against the principles of taste, the grandeur of magnitude, and simplicity of design, shall harmonize with the grandeur of strength in the material, and fitly call for the sombre appearance which it presents. What more noble object could have been offered to view in Trafalgar-square-what more characteristic of Britain and the British in a variety of aspects-than a cast iron statue of Nelson, 80 or 100 feet in height? The suitability of the site might indeed, with some reason have been questioned, inasmuch as the space is too confined to have viewed it properly, and is moreover out of character with that, or anything else that is simply grand. It would have frowned into insignificance the petty prettinesses around. Still, another site more appropriate might have been found, or at least a bronze or a granite statue of some 40 or 50 feet could have been erected, which would have been both a variety in that locality, and a novelty in modern times.*

IMPROVEMENT IN FIRE ENGINES.

Sir, In working fire-engines, under certain circumstances, a very striking and somewhat inconvenient illustration is afforded of the vis inertia of fluids.

This happens when the hose is led to the top of a high building, or has by other means a great altitude given to it. So long as the engine is worked and the ascending column of water kept in motion, the jet is delivered from the branch-pipe in the usual way; but, should the engine be stopped for a few minutes to shift the hose, &c., the pressure of the quiescent column of water cannot be overcome. On beginning again to work the engine, the delivery valves become set in an open position; the engine handles fly freely up and down as the water passes from one

The largest colossal statue in metal now existing is, I believe, that of Borromeo, on the borders of Lake Maggiore; and, if I recollect aright, it is constructed of copper sheets hammered into form.

only effect that can be produced. The vis inertia of the high column of water contained in the elevated hose cannot be thus overcome, but must be got rid of in another way. This is done by taking off the screw cap of the delivery orifice opposite that to which the hose is attached

or if there be but one delivery orifice by unscrewing the hose itself-when the water immediately escapes. The cap is then replaced, and the engine set to work de novo, when the water rises in the hose and is discharged in a jet as before.

This phenomenon is peculiar to fireengines with spherical air-vessels and separate valve chambers on Hadley and Simkin's patent principle, in which the valves are hung in an angular position. Different engines, even by the same maker, are more or less liable to this effect, some failing under a shorter column than others. This is especially the case in some country-made engines, in which the valves are so badly adjusted, that in some positions the engine will not work at all. Newsham's engines, with upright or hollow-shaped air-vessels and horizontal valves, are not liable to fail in this

manner.

At Streatham church, when struck with lightning, and at several other recent fires, considerable inconvenience has been experienced from the cause stated; and it has been customary to station a man at the engine to unscrew the cap and relieve the hose every time the engine ceased working, by which means much of the evil is obviated.

Removing the cap, however, under such circumstances, is a very unpleasant operation, and is not altogether free from danger; exposed as it is to a pressure from within, of from forty to fifty pounds upon the inch. Besides which, the strain upon the last thread of the screw, just as the cap flies off, is very severe, and very likely to prove injurious.

It is by no means necessary to incur these disadvantages, because it appears to me, that a very simple remedy may be provided; and in order to relieve the hose without removing the cap, I have proposed that a small cock, or valve, should be placed in the cross-arm or delivery main, immediately beneath the air-vessel, as shown in the accompanying figure.

A is the cross arm; B the delivery screw with the hose attached; C, the op

small cock, having about an inch waterway, opened or shut by the handle E. This handle is weighted, so as to have a constant tendency to keep the cock shut.

The advantages of this trifling addition to fire-engines would be very great. In the first place it would afford a convenient and effectual remedy for the evils of vis inertia, with much greater rapidity than removing and replacing either the hose or the cap. For, it is not necessary to discharge the whole of the water from the hose; a small portion will frequently suffice to bring the column within the power of the engine, which could be discharged in a second or two. In fact, it could always be accomplished between receiving the words of command "stop her" and "go on," however rapidly they might succeed each other.

In the second place, this cock would at all times enable the hose to be emptied instantaneously, preparatory to lowering it-to shifting its position, or to "making up."

I remain, Sir, yours respectfully,
WM. BADDeley.

29, Alfred-street, Islington.
September 23, 1842.

LIFE ASSURANCE.

Sir,-Kinclaven was right in supposing that the question I proposed on Life Assurances, (No. 989,) was not fortuitous. In truth it was sent me for a solution somewhat more than a year ago, and it was enunciated exactly in the same way as I sent it to the Mechanics' Magazine. I solved the question, and obtained the same results as those found

by your correspondents Mr. Scott and G. of Pentonville,* (so far as G has gone.) The condition in the question, of one-third of the profits arising from deaths going to the proprietary, appears to have been a stumbling block to G, and this most essential part of the question he does not answer; perhaps G may be connected with some of the Assurance Offices, and therefore did not choose to expose the secrets of the profession.

On Mr. Scott's solution I beg to offer a few remarks. He (Mr. S.) calculates from the data of the Northampton Table of Mortality, interest 3 per cent., that the single premium is 38-3861., or 381. 7s. 5d.; and that the amount of this sum for 20 years, together with the profits arising from the deaths, will just enable the Company to pay each surviving subscriber, at the termination of this period, 1007. But when one-third of the whole profits arising from such a source goes to the proprietary (for the expense of management, &c.,) the like premium from the same data, he (Mr. S.) calculates to be 44.0457. This will produce a present profit to the proprietary of (44'045—38:386) 5·6591. for each subscriber, or 5651. 9s., for the 100 individuals, and at the end of 20 years, at 3 per cent., this sum would amount to 1,0227.; which sum, if we could rely on the accuracy of the data, would be the profit that would go to the proprietary for their trouble of management, &c. But what a sad contradiction, the Swiss Table of Mortality gives to this imaginary gain, obtained from the Northampton data! Mr. Scott has calculated from the Swiss Table, interest at 3 per cent., that the single premium is 45.2577.; no part of the profits going to the proprietary. Hence, if the Swiss Table of Mortality tells the truth, the imaginary profit of 1,0221., produced from the Northampton Table, is converted into a positive loss of 2181. 4s. 3 d., besides the proprietary having nothing for their trouble. If the proprietary were to allow 4 per cent. their loss would be still much greater.

The Swiss Table of Mortality very nearly agrees with the Carlisle, and the Carlisle Table, with a slight modification, is used in the Equitable Assurance Office, and I believe in many other offices, so that it may be safely asserted

When I sent my last article I had not read over G.'s strictures on the enunciation, &c.

IVER M'IVer.

MR. BIRAM'S IMPROVEMENTS IN PADDLE-
WHEELS AND OTHER
CHINES.

ROTARY

MA

Sir, I feel exceedingly obliged to you for the favourable notice you have taken of my improvements in rotary engines, in a recent Number of your valuable Magazine; and I should be glad to make public, through the same medium, what I conceive to be the advantages of my side paddles over the common paddlewheel, as your notice extends merely to their construction.

From the oblique manner in which the vanes or floats enter and emerge from the water, they not only present less resistance to the water at those points, but they may be immersed double the depth of the ordinary paddle,† and therefore the same area of float may be made to act against the water with only half the breadth of wheel; the side plates counteracting the less efficiency of the floats from their obliquity, which would otherwise exist at the required point of action. The number of floats may also be reduced to one-half of those in the ordinary

There are a few misprints or mistakes, but so obviously such, that I scarcely know whether it is necessary to notice them.

Page 322, 1st col., 12th line from the bottom, the letters C B should be A B.

Page 322, 2nd line 2nd col., for "CB, fig. 1," read "A B, fig. 4."

Page 322, 31st line 2nd col., for "fig. 2" read "fig. 5."

Page 323. In the diagram, fig. 6, the letters E and F should change places.

Page 326, 2nd col., 3rd line from the bottom, for "AB" read "C D."

I would also observe, that the remarks made respecting the tremulous motion of steam-vessels being obviated by the stern propellers, apply more properly to the side paddles; for the stern propel lers, being constantly in the water, cause no tremulous motion whatever.

I consider that the depth the paddle should be in the water, at the load water line, should be half the radius of the wheel,

wheel, as I have found six floats quite as efficient as any greater number.

I am also of opinion that a propelling influence is exerted upon the vessel, from the acting floats forcing the water against the inclined plane which the after end of the vessel presents to the line of motion. The two oblique lines, a a, represent the position of the two floats in full action, and the arrows the direction of the current in the water, created by the revolution of the wheels. The increased depth

an angle of from 60° to 70° with the vessel's path; in which case, the action of those vanes or floats immersed the deepest in the water, (and which, when one propeller only is employed, creates a rotary tendency in the vessel,) would act upon the water more to the rear, and by so much increase the speed of the vessel. This position, by throwing the axles of the propellers nearer together, would also be more favourable for the application of the power.

In the following diagram, p represents the position of the propellers, and the angles they make with the vessel's path.

of the paddles, and reduced breadth, (being thereby nearer the centre of motion,) offer a considerable advantage at sea, upon the heeling of the vessel, the paddles being so much less likely to work out of the water.

I would make a few remarks respecting stern propellers. In the course of my experiments I have observed, that the action with only one propeller, placed in the centre of the stern, produced a tendency in the vessel to a circuitous path, caused, as I suppose, by the greater resistance which the under side of the propeller has to encounter from the extra pressure arising from the greater depth of water. This would not be the case, possibly, to the same extent with vessels whose length is so much greater in proportion to their breadth, as steamers generally are, compared with the boat with which I experimented; but still, trifling as it might be, it would be effectually remedied by employing two propellers, with the leaves inclined, and the wheels turning reversewise to each other. This unequal resistance to the propeller, from its varied depth in the water, also leads me to believe that increased efficiency would result by placing the propellers so, that their plane of motion should be at

I have just received the last Monthly Part of the Mechanics' Magazine, and the description of the Great Britain steamer, with the mode of propelling her. I feel quite confident that, with one revolution of a propeller upon my plan, having the extremity of the floats at an angle of from 56° to 60° with the plane of motion, the vessel would advance as far, as with five revolutions of the propeller there described; thereby rendering unnecessary the large driving-wheel and its attendant straps, the wear and tear of which must be very considerable. Nothing could be more easy than to test the correctness of my assertion, that is, by having a model of each propeller, and causing them to revolve in a vessel of water in which were sprinkled a little bran, small pieces of paper, or other floating particles, when the comparative velocity of the current which each would create, would convince any one how very unnecessary are driving-wheels and straps to stern propellers properly constructed, and that the power might be applied direct from the engines to cranks upon the propeller shaft; the number of strokes per minute of the engine giving quite a sufficient number of revolutions to the propeller.

I have just had constructed two wheels of sheet zink, for the purpose of testing the principle I have laid down as to the relative speed of wheels with vanes at different angles, propelled by fluid, and their power of measuring the velocity of such fluid, or of bodies to which they may be attached passing through any