which is, that it upsets his own argument in the preceding paragraph respecting the syphon, and tends to confirm his opponent's statement on that head, namely, respecting the difficulty of drawing water by means of suction without the assistance of the pressure of the atmosphere.

Mr. V. also contradicts his own statement respecting the means by which the 32-feet upright column of water is confined in the tube. In one part he says, "It is the upward pressure which confines the water in the tube;" and in another, "Here again he (Ed. V. R.) is perfectly right, the contents will not quit the pipe, the whole column remaining as though the bottom of the pipe were plugged, which is sufficient proof that it was not either balanced or supported in any way by the water below."

Really, Sir, after these precious samples of Mr. V.'s ability in using the goose-quill," it were beneath criticism to follow such a reasoner further. I will at present only notice, that his next object is an attempt to fix an error on the "sober calculation," which he does by squeezing in for the odd decimal parts, and by rejecting 10lbs. the weight of the gallon of water which stands above the moveable sucker of the common liftpump; "the weight of this water," he says, we have nothing to do with," in depressing a pump-handle. Now, Sir, it is evident, that it would be impossible to get out any water with the common lift-pump without lifting this water, ergo, we have nothing to do with the weight of the water absolutely lifted. Quod est absurdum. Therefore, we have to do with it. Yours, &c.

66

June 28, 1831.

ED. Vocis Rationis.

P. S. Since Mr. Valentine (in which, I grant, he is backed by the Old School) appears so strenuously opposed to my theory respecting the lifting of the whole 32-feet upright column of water by means of the moveable sucker; and since I have hitherto reserved my proofs in case the matter should be "disputed" (see note, No. 401, p. 102); and since it has been so learnedly disputed; it may not be amiss in this place to furnish one of the learned disputers with a small dose (as he appears not much to relish such things) by way of one of my proofs or reasons for rejecting the old theory. Sup

13

pose a cylinder, 32 feet in length, and 4 inches bore, furnished with a solid moveble piston, air-tight; depress the piston nearly to the bottom of the cylinder, and then plug the bottom of the cylinder so that the surfaces of both piston and plug may be in close contact. In this position there is nothing between the plug and piston. Now, draw the piston up, you will find that it will require great force to do it; and if you lose hold of the piston-rod when drawn up, it will fly back as if discharged from a musket (this a person may often experience in cleansing a gun-barrel when the touch-hole has been accidentally stopped, and some water lies above the cleansing-piston, which has the effect of making it airtight). Now, it is evident in the above case, that the solid piston has only the pressure (beside friction) of the external air to lift, in which experience proves that the greater force is required. Again, suppose the piston in its original position at the bottom of the cylinder; take out the plug, and admit the air; in this case experience proves that the piston may be drawn up with great ease, and will not fly back. Now, it is not very material in this respect, whether we admit air or water in lieu of it to the bottom of the cylinder, for both are fluid; and in the latter case experience proves that we can raise a piston with much greater ease when air or water (which comes in lieu of air) is freely admitted by the bottom of the cylinder, than we can if neither water nor air is admitted. But according to the old theory, the labour ought to be greater in the latter case than in the former; for, in the first case there would be only the pressure of the air to be lifted-and in the other case (according to the old theory) there would be the additional increasing weight of the 32-feet upright column of water, i. e. in the first case there would be only the weight of atmospheric pressure, viz. 1884lbs. and in the latter case 358 lbs. (allowing 170lbs. for the weight of the 32-feet water in cylinder), and yet experience proves that it requires less force to raise the supposed greater than it does the less weight, which is absurd. The above is also confirmed by the labour being increased in case of accidental stoppage of the holes at the bottom of the suction-pipe; or, as Mr. Valentine says, by too small a suction-pipe." ED. V. R.

SAFE REMEDY FOR RATS.

Sir, I have no doubt but that you must, as well as myself, have long since remarked with mingled feelings of astonishment, disgust, and regret, the facility with which any individual man, woman, or child, can obtain poison (generally arsenic or oxalic acid) at the chemists and apothecaries, by merely saying that it is to kill rats, or clean boot-tops!! It is sufficient that the parties do not candidly avow that they want "the two penn'orth of arsenic" to poison either themselves or some body else, for it to be served out to them as a matter of course!!! I could show you a list of 38 cases of murder, suicide, or accidental poisoning, which have lately occurred in this country, which had they taken place in any other country in Europe (not to mention France), would have subjected the vendor of the poison to very heavy inflictions of fine and imprisonment. Here, all that these real aiders and accomplices in crime have to fear, is a slight censure of a coroner's jury, who, forsooth, "cannot help expressing their regret that such deadly poison should have been sold (perhaps to a child!) with so little caution." The apothecary, however, has sworn that he did not know to what purpose the arsenic was intended, and that he wrote "poison" on the packet. Innocent, simple soul! how could he suppose that it was bought for any other purpose, when the little girl positively told him, it was "to kill rats!" Besides, he wrote "poison" on the paper-quite a sufficient check and spell upon those who wanted poison! And after all these

66

precautions," why should he, good man, be expected to forego the profit of his trade upon two penny worth of poison! To the hulks, to the hulks, say I!But I must proceed to the purpose of this letter, which is, to acquaint such of your readers as may be troubled with rats, that they may poison them with a substance which is not poisonous, and with which there is no danger of their dogs, poultry, pigs, children, or neighbours, being any of them poisoned.

Let those who wish to poison rats without applying to the chemist, intimately mix a pound of plaister of Paris (in its unslacked state) with an equal quantity of oatmeal. Let him place this within the reach of the rats-they will eat of it

eagerly and without being deterred by any bad taste. By the humidity contained in their stomachs, the plaister of Paris will "set" and form an indigestible, hard mass, which will in fact present upon dissection a good cast of the rat's stomach, and speedily produce a kind of Aldermanic death, i. e. by irremediable indigestion.

Neither dogs, poultry, children, nor neighbours, will lap or pick up a dry, pulverulent mixture like this. I cannot quite answer for pigs; but I am pretty sure that neither a quadruped nor a biped hog, whatever might be his appetite, would be inclined or capable of swallowing enough of such an inconve nient" exhibition" to occasion the fatal indigestion which I know it will infallibly cause in rats and mice. Any how, it must be evident to most men, that no such danger can attend the employment of plaster of Paris, as of arsenic, aux vomica, or corrosive sublimate, for the purchase of which, moreover, there would no longer be any pretence.

Rats are very intelligent animals; so the better to beguile them, it is well to begin by giving them pure oatmeal. Those who first discover and partake of it, will speedily communicate the glad tidings to their relatives and neighbours, who may then be swept off all at once; as we shall soon have the pleasure of seeing occur to the far more rapacious, mischievous, and detestable hiped boroughing (burrowing) fraternity.

I have not had an opportunity of trying the mixture of oatmeal and plaster of Paris upon the beetles which infest kitchens, but I think it will be found efficacious.

Yours, &c. FRANCIS MACERone. London, Sept. 1).

FALSE ALARM OF FIRE, OCCASIONED BY A SINGULAR ATMOSPHERIC PHENOMENON.

Sir,-About half-past four o'clock on Sunday morning, the 25th instant, I was called up, with information that a

It was on an analogous principle that the ancients, especially the Greeks, used bull's blood as a poison, which being drank fresh drawn, formed an indigestible coagulum in the stomach. In this manner, we are told, that Midas, Dioscorides, Hannibal, and a multitude of others, terminated their existence; a rather round-about method this, compared to the inodern Prussic acid operation.

large fire had broken out, in the direction of Whitechapel.

On looking through my chamberwindow, which faces the West, I saw the moon shining most beautifully, and my room filled with her silvery beams; but on the buildings opposite, I could plainly perceive the reflection of a strong red light, which I naturally concluded to be occasioned by the fire. Having hastily dressed myself, I proceeded along Fenchurch-street, from whence, the horizon in the direction of Whitechapelchurch, appeared illuminated by a dense red light, covering about the same space, and bearing an exact resemblance, to that occasioned by an extensive conflagration.

On reaching the end of Fenchurchstreet, and endeavouring to ascertain, as near as possible, the situation of the fire, I found myself completely baffled; the reflection having spread considerably, and instead of being confined, as at first, to one spot, it began to be inore generally diffused over the horizon. It then occurred to me, that the appearance I witnessed was the effect of atmospheric phenomena; and, on reaching Aldgatechurch, my suspicions were confirmed, by there finding collected, the firemen who had been drawn to the spot by the same cause as myself.

After I had watched the sky for some time, from Aldgate, the redness appeared to separate in the form of streaky clouds, showing the grey sky between, presenting, for some time, a magnificient spectacle.

The appearance, at the commencement, was so completely similar to that of a large confiagration, that numbers of the firemen, hastened with their engines at full speed towards the eastern part of the metropolis, as also did a great number of spectators, who naturally enough concluded the fire to be of unusual magnitude.

What rendered the phenomenon somewhat more extraordinary and unexpected, was, that the sun did not rise till six o'clock that morning, while this singular appearance was presented so early as half-past four.

As I find the phenomenon was seen, by a great number of persons residing in, and near the metropolis, I hope some of your readers will be able to give a more particular account of its appear

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EXPEDITIOUS

SHORTENING A RIVER
MODE OF EXCAVATION.

We extract the following interesting account of a recent shortening of the great River Mississipi, between New Orleans and Louisville, from a New York paper:

"The navigation has been shortened about 42 miles by cutting off two bends in the river. The first bend is that where the Red River empties itself. The distance round the bend was 18 miles. Captain Shreve, the superintendant for improving the navigation of the Mississipi and Ohio, commenced making an excavation across the peak of land at the narrowest point. The object was effected by cutting a canal 17 feet wide by 22 feet deep. The water was let through the canal about the 28th of January, fourteen days after the commencement of the work. In two days the water had excavated a channel to such an extent, that the steamer Belvidere passed up through it. On the same day the United States steamer Heliopolis passed up the same channel. Since that time the steam-boats have all passed through the cut up and down. In five days it was the main channel of the river, about half a mile in width, and of equal depth with other parts of the river. The excavation was made by the steam-boat Heliopolis in an unexampled and expeditious manner. By laying the boat's head on shore two scrapers of large size, were worked by lines from four windlasses on the main-shaft of the boat two lines to each scraper, one a sixinch line to haul the scraper into the bow of the boat; the other, a three-and-ahalf inch line passed through the leading block on shore as far out as was necessary, and fastened to the back-end of the scraper to draw it out. In this manner the scrapers were kept in continual operation, loaded and unloaded by their own motion attended by two men each, moving the earth out, and throwing it into the river, where it was washed away at the rate of at least a ton weight per minute. The other bend 200 miles above Natchez, which has been cut off, is not so perfect a navigation. The distance ronnd it is 24 miles. That channel has been formed by cutting a small ditch through, two years ago. Last fall the timber was cut off the

;

banks. Six or eight steam-boats have passed up through it. It is believed, that it will wash this year to such an extent. that it will be the main channel of the river next year. The saving in the navigation will be equally as great as that at the Red River."

MISCELLANEOUS.

Cultivation of the Tea Plant in England.-Mr. S' Rootsey, of Bristol, in a letter to the Bristol Journal, says, "Having found the Chinese green teaplant to be more hardy than some other shrubs which endure the open air in this neighbourhood, I have tried it upon the Welsh mountains, and found it to succeed. I planted it in a part of Breconshire, not far from the source of the Usk, about 1000 feet above the level of the sea, and higher than the limits Of the native woods, consisting of alder and birch. It endured the last winter, and was not affected by the frost of the 9th of May. It has now made several vigorous shoots, and I have no doubt of its thriving very well in time."

Miniature Watch.-Mr. Arnold, the eminent watchmaker, presented a watch to the late King, which is now in the possession of Queen Adelaide, which does not exceed, in size, half-a-crown, and weighs altogether only 5 pennyweights, 7 grains. The hour hammer weighs only half-a-grain, and the 'great wheel and fuzee 23 grains!

Paganini.-Dr. Bennati, of Paris, in a paper communicated to the Academy of Science, attributes the extraordinary musical powers of this wonderful fiddler to a peculiar conformation, which enables him to bring his elbows close together, and to place them one over the other-to the circumstance of his left shoulder being higher than the right to the slackening of the ligaments of the wrists-and to the peculiar suppleness of his fingers, which he can move at pleasure in any direction.

Mr. Gurney's Steam-Carriage has ceased to run 2) between Cheltenham and Gloucester. The stoppage

is attributed to the circumstance of the road having been newly Macadamized, and to the difficulty of overcoming the additional obstruction thus occaioned.

Screws.-Mr. Adcock, in the course of a recent lecture at the Manchester Mechanics' Institution, exhibited a screw of the manufacture of the late Mr. Maudsley, which in 4. feet 6 inches of length gave an inclined plane 1800 feet long. This screw had 50 threads in an inch, and yet did not throughout its length deviate from accuracy more than the 1500th part of an inch.

The Great Tom of Lincoln exists no longer-in its entire state at least. Its tone has been long impaired, and is now, by an accident, ruined beyond redemption. Some workmen were lately driving a wedge in the progress of tracing a flaw, when a large piece of the rim or skirt, weighing 6 cwt. and about 8 feet long, broke off. Tom, when entire, weighed nearly 884 cwt.; but there has been broken off at different times about 9 cwt.

Sir Humphry Davy.-Lady Davy, some time ago, gave £100 for the use of the University of Geneva, in token of her grateful remembrance of the honours paid to the remains of her late illustrious husband by the public functionaries of that city, in which he breathed his last. The Professors of the University have very properly resolved that the interest of this money shall be appropriated to the establishment of a chemical prize, to be contended for annually. "We have seen the first medal that has been struck for this purpose," says the Times," and a most creditable instance it is of the state of the arts at Geneva. One side commemorates all the labours of

Davy that can be made the subject of emblematica! description, such as the composition (decomposition?> of the alkalis by the Voltaic pile, the safety-lamp, the (unrolling of the) Herculaneum manuscripts, &c.; on the reverse is a wreath formed by the plant which bears, after him, the name of Davya, with the inscription, Offerté par l'Academie de Geneve à Lady Davy.' In other years it will have the name of the successful candidate for the prize." The Times farther observes, "This forms a pleasing contrast to the conduct of the chapter of a certain wealthy cathedral (in the west end of the town) who after expressing an earnest desire to have within their walls some memorial of their illustrious countryman, ultimately refused to admit a tablet of very moderate dimensions, except on payment of a charge which would have exhausted the humble fortunes of most of the philosophers of either ancient or modern times."

Lacaille's Observatory.-Lacaille had an observatory at the College Mazarin, or des Quatre Nations, part of which is now the Palace of the Institute. Since, a long time, it had been without observer or instruments; under Napoleon's reign it was demolished. Lacaille never used to illuminate the wires of his instruments. The inner part of his observatory was painted black; he admitted only the faintest light to enable him to see his pendulum and his paper: his left eye was devoted to the service of looking to the pendulum, whilst his right eye was kept shut. The latter was only employed to look to the telescope, and during the time of observation never opened but for this purpose. Thus the faintest light made him distinguish the wires, and he very seldom felt the necessity of illuminating them. Part of these blackened walls were visible long after the demolition of the observatory, which took place somewhat about 1811.-Professor Mohl.

Novel Application of Horse Power.-Mr. Israel Abrahams, in the vicinity of this town, has a horse that will of its own accord pump a sufficiency of water for all the other horses on the farm. We have witnessed him, when turned loose in the farm-yard, go directly to the pump, take the handle between his teeth, and throw the water with as much regularity as a man would until he would pump enough for his companions and himself, when he would drink and deliberately retire. No pains were ever taken, or means used, to teach him a business which proves a great accommodation to himself, and relieves his owner of considerable trouble.-Centreville Times.

Steam Travelling.-The steam-packets between Liverpool and Dublin are now conveying persons of the labouring class at the charge of sixpence per head! On one day lately three steamers landed a thousand passengers each on the pier-head at Liverpool.

INTERIM NOTICES.

R. H.-declined.

Communications received from Mr. Barrett-J. B. -Mr. Rough-Mr. Dewhurst-A Young Navigator -Lambda-Mr. Crathorue-Mr. Reed-A Constant Reader.

ERRATA.-P. 470, vol. xv., c. 1, 1. 22, from the bottom, for "this vapour occupies several hundred times more space," &c., read this vapour occupies several times more space," &c.

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, Wine-Office-court, (between 145 and 146) Fleet Street, where Communications (post paid) are requested to be addressed.

M. SALMON, Printer, Fleet Street.