very convenient bags, with which they are often provided, enable them to save also most of the minor articles, which would probably otherwise become a prey to the flames. None but members of the brigade are allowed to enter the house; by this wise regulation, men of a bad character are entirely prevented from exercising their disgraceful industry on such occasions, while the order and method with which the praiseworthy exertions of the fire-brigade are conducted, are certainly productive of the greatest benefit to the poor sufferers. It is but justice to state, that on all occasions these exertions meet with due encouragement from every one capable of appreciating the self-devotion and generous feelings of the spirited citizens forming the honorary fire-associations.

Before I conclude, I beg to be allowed to make one more reflection. It sometimes happens in this country, that fireengines cannot be put in action immediately on their arrival, because no water can be procured, the man who has charge of the key of the water-plugs not being on the spot. Now, in Switzerland, two or three keys are distributed to an equal number of persons living near the house where the fire-engines are kept; so that, in want of one key, there may always be procured another in any case of emergency. It is evident that the application of this principle to the water-plugs of the metropolis would be as beneficial as easy. It would, indeed, be quite needless for me to dwell on the advantages which would undoubtedly accrue from such a practice being adopted. I shall, therefore, only add, that

I have the honour to be, Sir,
Yours respectfully,
P. OBER.

Twickenham, July 20, 1838.

SINGULAR FACT IN FALLING BODIES.

Sir, I have observed that a piece of stiff writing-paper, three inches long by an inch wide, held up as high as a man can reach, and extended between the fore finger and thumb of each hand, and then let loose in a room, when the doors and windows are shut, will always revolve on its long axis. This fact I mention in the hope that, in this age of mental exercise,

In all such observations, the annual motions must be allowed for, and so reduced as if there were no such motions. Let this be done, and let A B be an arc of the Earth; V, Venus; and S, any point in the sun with which V is in conjunction, as seen from B; but from the observer at A, the point S appears in the direction AS, and Venus in the direction A V, where V will fall on a different part of the sun. Here angle A V B is the parallax of Venus, and angle ASB that of the sun. Now angle SAV is the only observed angle, and its position is unknown; whence A S was treated as if parallel to B S, making the alternate angle AV B = angle SAV, and whence the sun's distance as if infinite; but since the sun has a parallax, AS and BS must meet at S, and form a triangle A S V, whose outward angle, A V B, is greater

than either of the inward angles, SAV or S,.. the angle S is equal to the angle A V B, less by angle S A V, which gives the difference of the parallaxes, and not the parallax of either the sun or Venus. Thus treating A S as parallel to BS, the angle AV B measures too little; and hence A V or B V are too much for venus's distance; which, compared with the known ratio of the distances of the primary planets from the sun, make their distances and magnitudes too great: but if S was a fixed star, then A S would be parallel to B S, and angle S A V, and angle A V B would be equal, and would be the correct parallax of Venus. The ancients found the earth's distance from the sun to be 81 millions of miles, and this I find correct; and am, Sir, your humble servant,

May, 1838.

WILLIAM SHIRES, Teacher of Mathematics.

MILLS'S MERCURIAL PUMP NOT NEW, AND USELESS.

Sir,-Perhaps it would be too much to expect that every projector who may send his little nursling to encounter the rough ordeal of your Magazine, should previously be conversant with the history of the branch of science to which it may belong; nay, even the most absurd pretension to originality may be treated with indulgence, provided it be put forward with a due degree of modesty and diffidence; but the case is otherwise when we are told that a learned lecturer on natural philosophy, who ought, ex officio, to be deeply read in his vocation, has adopted the invention as a class-subject, and edifies his pupils by a model of the discovery!

It is almost needless to say, that this observation bears reference to Mr. Mills's account of his mercurial pump, contained in your 776th Number, page 190. Had Mr. Mills read an article on pumps in the Encyclopædia Britannica, (which book I particularize because there is scarcely any person to whom it is not accessible), he would have soon found that he has not a single particle of claim on the pump he has so charitably adopted as his own ;-that it was invented and abandoned for its many defects upwards of a century ago;-and that the only difference between the pump there des

cribed and that invented by Mr. Mills is, that the arrangement of the parts is slightly different,-the moving part in Mr. Mills's being an empty, unweighted, unsteady vessel; while in the original" invention (by Mr. Haskins) the vessel containing the mercury, rendered steady by its great weight, is the moving part; -the latter arrangement being so greatly superior, and so much more elaborately contrived, that it is an almost unavoidable inference that the plan used by Mr. Mills was first tried, and the other afterwards adopted as an improvement upon it. But, as if to deprive Mr. Mills of the loop-hole of escape which even this slight difference of arrangement might afford him, the description of Haskins's pump concludes with the following remark :— "It is on precisely the same principle as the cylinder bellows described under the article Pneumatics;" and the cylinder bellows, so referred to, is the exact counterpart of Mr. Mills's pump, the arrangement being there not so objectionable.

But the concluding remark in Mr. Mills's communication is of such transcendent genius, that it throws the rest far into the shade: he says, that one advantage possessed by his (?) pump is, that "for every inch of stroke of the handle K, the water will be raised one foot high!" This piece of unmitigated absurdity proves, as clearly as the noonday, that Mr. Mills has seen the description of Mr. Haskins's pump, and has copied it as his own invention, without understanding its principles: in the said description it is stated, that for every inch difference of height between the inner and outer columns of mercury, there must exist a difference of a foot in the columns of water, the former being twelve times heavier than the latter. Now, does not the sentence from Mr. Mills's letter, quoted above, furnish internal evidence that this part of the description of Haskins's pump must have been travestied in Mr. M.'s brain, without his having understood its meaning? else, why should he adopt one foot and one inch-13, and not 12, being now the acknowledged specific gravity of mercury ?

In fine, although Mr. Mills's model may form a very pretty squirting-toy for Mr. Grier's lecture-table, it is equally valueless, whether as an original invention or as a practical machine.

NAUTILUS.

Sir-From the non-appearance of my letter of the 3rd inst., respecting Mr. Mills's pump, I conclude that you considered it anticipated by Mr. Baddeley's communication on the same subject in No. 778, page 231. I freely acknowledge that Mr. B. was fully entitled to the preference, as well from priority in the date of his letter, as from his known experience in the world of hydraulics. I took, however, quite different ground from him; he confining himself to objecting to the practical efficiency of the pump, while I directed my remarks to its total want of originality; in fact, all the objections adduced of Mr. Baddeley may be found in any of the many treatises wherein the pump of Haskins is described.

There is, however, one most extraordinary blunder, into which Mr. Baddeley has fallen, and which I sincerely regret, as it may afford a peg to Mr. Mills or his friends whereon to hang an apparently successful answer to his letter. It is that part wherein Mr. Baddeley says that Mr. Mills's pump is of the lifting, and not of the suction kind, as stated in Mr. Mills's description.

Now, that the contrary is the case, is an axiom so palpable to any one who has glanced at the rudiments of hydraulics, that to attempt to prove it by any serious argument is almost puerile; but, when such an authority as Mr. Baddeley is supposed to be, writes it, not as a random assertion, but as a grave accusation of want of correctness in description, a few words in proof of his egregious mistake may be excused.

A lifting pump, then, is that wherein the piston acts entirely beneath the surface of the water to be raised; for, if the piston act in the least above such surface, the pump partakes of the suction kind. Ordinary pumps, with a valve in the piston, are of this mixed nature, -the water beneath the piston being sucked, or supported by atmospheric pressure, while that above the piston is lifted.

Now, it is evident, that in the mercurial pump, decscribed at page 190, the piston being 30 feet above the surface, it is, in its up-stroke, altogether of the suction kind, and, in its down-stroke, of the force kind: the term lifting force-pump, which Mr. Baddeley has conferred on it, is, therefore, glaringly wrong; while the

We copy from the Manchester Guardian the following account of a very successful experiment made on the Duke of Bridgewater's canal with Mr. Ericsson's propellers, described in our 751st Number. The account is defective and erroneous in many particulars, and in none more so than in the ascription of all "the merit" of the affair to Messrs. Robins and Co. (the well-known carriers), and the apparently studious omission of the name of the ingenious and indefatigable inventor, Captain Ericsson. We have subjoined, therefore, some notes which may help to set the matter in its true bearings before the public.

As our American neighbours would say, we are going a-head" in the use of steam as a locomotive power. But a few weeks ago we noticed the starting of a small steam boat to ply on the Irwell, with passengers, between this town and Warrington; and we have now to announce the application of steam to carriers' canal boats for the transit of goods between this town and London. In canal navigation in this country, a long period of time has elapsed since any alteration or improvement of any great importance has been made. The boats are of the same construction, and so inartificial is the mode of working them, that the only means in practice, at the present day, for propelling them through the immense tunnels, of which one is nearly a mile in length and another three quarters of a mile, is for the boatmen to lie on their backs on the tarpaulin which covers the goods with which the boats are deeply laden, and, by pushing their feet against the roof of the tunnel, work the boats onwards at a tediously slow rate, with great labour and fatigue, amidst the smoke from the boats' chimneys or funnels, which, to any one unused to its effects in a long tunnel, would seem wholly unendurable. This is what the boatmen term "legging through;" and in this way

every boat-load of goods is worked onwards through the tunnels on every great waterline of internal navigation in the country. The first application of steam on canals has been made, not on a new form or construc. tion of boat, nor even on an iron boat of similar form, but on one of the long narrow canal boats, with sharp stem and stern, which had for some time before been plying on the canals in the usual way. The experiment which has been tried, at little cost, and which, at best, is an imperfect one, has, however, been eminently successful; and there appears very little doubt that its results will be a revolution as complete in canal navigation as the introduction of marine steamers has worked in our coasting packets. The merit of making this experiment belongs to Messrs. Robins, Mills, and Co., carriers, of London, and of Castle Field Wharf, in this town. Into one of their canal boats, near the stern, they introduced a small high-pressure marine steamengine, of only four horses' power, to which a boiler that had been used for one of the locomotive engines on the Liverpool and Manchester Railway was adapted (1.) As the narrowness of canal tunnels and the injury likely to result to the banks from the use of side paddles must always have thrown a difficulty in the way of applying steam power, in the ordinary mode, to canal navigation, it became necessary to substitute some paddle which should not be in the way, while it should not be liable to the objection of injuring the banks. This difficulty has been surmounted, as it seems to us, very satisfactorily and completely, by an ingenious application of the principle of the old fish-tail paddles (2.) These paddles are placed at the extreme stern of the boat, and this terminating in a sharp point, it was necessary to lengthen the boat, and make a square box to contain the paddles (3.) They consist of two small wheels, placed side by side, not working parallel to

(1) The boiler is not one that has been used for locomotive engines-it is one invented by Captain Ericsson, and of quite a peculiar construction. It is besides only 5 feet 10 inches long, while locomotive boilers are never less than 12 feet. The cylinder is 12 inches in diameter, with a 10-inch stroke, making about 70 strokes per minute; the steam always kept at 30 lbs. per square inch. The scientific reader will allow that such power is good measure for "four horses."

(2) The propeller is by no means on the principle of the "old fish-tail paddles." See description in Mechanics' Magazine, No. 751. The Guardian's process of reasoning seems to be this; the tail of a fish is (commonly) behind the rest of its body, Captain Ericsson's propeller is placed behind; ergo Captain Ericsson's propeller and a fish's tail are very much alike. By the same sort of logic it might with great ease be shown to be very like the famouos pigtail at Charing Cross.

(3) The boat has not been lengthened. A square

the boat, but transversely, and revolving contrary ways (4.) The paddle-boards or plates of iron, of which there are six on each wheel, have an inclination of about 45°. When in action, therefore, it will be seen that, as one wheel of paddles strikes the water on the starboard side of the stern, the other strikes it on the larboard, thus producing an action on the water resembling that which sailors call "the double scull," and which is the best effort of art that we have seen in imitation of the mechanical action of the tail of a fish when swimming (5.) The defects of the present experimental engine, &c. seem to be rather in its adaptation and arrangement than in itself. In the first place, we should think a more powerful engine necessary to the fair development of the power of steam in this species of navigation, considering the great length of the boat and the bulk and weight of its cargo, which is probably eleven or 12 tons (6.) Then we have no doubt, that that form of boat which has hitherto sufficed for the slow dragging of horses and a towing line, is not precisely the shape and build, nor, perhaps, is timber the best maAgain, terial for canal steam navigation. it appears to us that the engine was rather too far from the paddles to exercise its full available motive power (7.) But these and several other points, into which we have not time to enter, will, doubtless, receive a full and sagacious consideration from scientific and practical men when once their attention is directed to the subject (8.) That the time for this, we think, bearing in mind the power and force of competition in every branch of trade and mode of communi cation, cannot be far distant. But to return to the Novelty, which is the new name the

piece of wood has been attached to the stern part, but which does not project more than 10 inches further aft than the point of the stern of the ordinary flyboats.

(4) The paddles are not placed "side by side." See above Number of Mechanics' Magazine.

(5) The paddles do not " strike the water;" the propulsion being perfectly uniform, a gradual sliding of the water takes place from the stern.

(6) The engine is by no means a defective one, nor has it been found not powerful enough; on the contrary, its power is full 20 per cent. too great for the paddles, which ought, in point of fact, to have been much larger.

(7) The power of the engine is communicated to the paddles by means of a straight shaft of about 12 feet in length. Does the Guardian suppose that if this was reduced to 6 feet the power of the engine would be increased?

(8) The inventor, Captain Ericsson, being neither scientific nor practical!-and all "the merit" in the case consisting in the introduction by Robins and Co. of the "old fish-tail paddles!" if our cotemporary will but condescend to advise with some of the many "sagacious, scientific, and practical men" to be found in his own neighbourhood, he will be surprised to find how little he really knows about the whole matter.

boat received when from a [tow] liner she became a steamer, the first voyage she made very recently from London to this place with very considerable success. Like her great prototypes, the Great Western and the Sirius, a log was kept of her rate of steaming during this her first outward voyage; but we have not been able to obtain a sight of this log, and can, therefore, only very generally notice her performance, which, we understand, was at the rate of nearly eight miles per hour. She left Paddington on Thursday week, at noon, with about eleven tons of goods, but was detained for several days on the Grand Junction canal, waiting her turn to proceed: notwithstanding this delay, she reached here about half-past three o'clock on Wednesday afternoon last, without having sustained the least injury, except that, having been lengthened, she was a little too long conveniently to pass some of the locks; and the result was, that her paddle-boards were a little bent and put out of order. They were speedily put to rights; and, on Monday last the proprietors, with a party of friends, proceeded with the boat on an excursion down the canal, we believe as far as Runcorn, when her speed was tried, with the favourable results already noticed. On Monday evening she took on board a cargo of bale or pack goods for London, and, we believe, started on her homeward voyage the same night. We understand that when going at the rate of eight miles an hour she does not occasion the least swell. It is anticipated that she will be able to deliver goods in London in three days from her departure from this place. On one occasion shortly before her first canal voyage, the Novelty towed the city barge, on board of which were a hundred and fifty gentlemen, up the Thames as far as Teddington Lock, at the rate of about eight miles an hour; and her performance then gave the highest satisfaction to all who witnessed it.

Since penning the preceding notes, we have seen a subsequent notice in the Guardian, which we also insert, in which we are glad to observe tardy justice is done to Captain Ericsson, and the character of the improvement is a little more correctly appreciated. It is not a little amusing, however, to note the pertinacity with which our contemporary sticks to his fish-tail resemblance, while in the same breath he does his best to show that there is no resemblance at all. (Second notice in the Manchester Guardian.)

In an article under this head in the Guardian of Saturday last, we noticed the

first down voyage to this town from London, through the canals, of a steam-boat named the Novelty.

We have already stated that the Novelty is the hull of an old canal boat. Her form, to those unacquainted with the build of these boats, will be better understood when we state that her length is about 74 feet, with a seven feet six inch beam; she is heavily constructed, and when loaded draws about two feet water. We noticed that her engine was high pressure, and of four-horse power, supplied with steam from a small locomotive boiler. The boat is fitted with a species of paddles, already described, but perhaps better known as "Ericsson's" propellers, in substitution of the side paddles of the old steamers, which are constructed so as to propel without raising a surge injurious to canal banks, and so as to pass through the narrow locks with ease and safety objects hitherto unattained, and deemed impracticable. The main pесиliarity of this invention is the construction of the paddle, so as to secure an action resembling that of a fish's tail, or of a perpetual sculling through the water. The difference between the operation of these propellers and that of the fish or double scull is, that instead of the force being alternate from side to side, the propellers' strokes upon the water are simultaneous. As these propellers work with the greatest effect when submerged, no waste of power is incurred, and no shaking motion communicated to the boat. When in motion, with her propellers submerged, there is little to distinguish the Novelty from other canal boats, the old wooden funnel being retained; there being little smoke, as coke is the fuel consumed: the engine and boiler being out of sight, and the only variation in her form being the elongation and widening of the stern, about 14 inches, with the addition of a slight stage for the helms

man.

We noticed the fact of an experimental trip having been made by this boat on Monday week upon the Duke of Bridgewater's canal. The party on board consisted of some of the principal canal proprietors and water carriers in this town and neighbourhood, and their friends. The Novelty started from the Manchester end of the canal about six minutes before one o'clock; passed the Worsley branch at twenty minutes past one o'clock, and reached the wharf at Altrincham at half-past two o'clock, having performed the eight miles in one hour and 36 minutes. The speed of the boat, and the fact of no towing horses being visible, caused no small astonishment to various rustics on the canal banks, and some of the more cunning of these people, her