WRIGHT'S IMPROVED GAS-STOVE. Sir,-Having invented and practically applied a modification or improvement of the gas-stove lately patented, the result of which has equalled my fullest expectation, I am induced to lay the same before the readers of your valuable Magazine, from a conviction that it only requires to be well known to be generally adopted.

It combines three most useful properties, viz. portability, lightness, and cheapness at the same time it has none of the ill effects so justly attributed to dry air arising from the old gas stove. The material is entirely sheet-iron (with the exception of the copper gas-ring and fittings.)

The annexed drawing (see front page) is a vertical section of the stove now in action. A is an outer case of cylindrical form, inclosing an inverted cone B, around the lower part of which the ignited gas plays from the hollow perforated ring C. There is little novel in the general principle of these three portions of the stove, but my improvement consists 1st, in the addition of a smaller cone D, supported within the larger, leaving a space between the two for the current of air: 2nd an annular vessel K, containing water through which the hot air must pass in its passage through the stove; and lastly above the vessel K., and between it and the damper, is placed a circular plate L rather larger than the orifice in the water vessel. The use of this plate will be

seen.

The gas being ignited through an opening for that purpose, the cone immediately above the jets gets heated; this by rarifying the air within, causes an upwards current through the stove; the external air now rushing in is divided by the point of the lesser cone, and compelled in its passage to pass against the heated sides of the larger cone.

It now rises through the opening in the water vessel, and striking against the plate passes over the surface of the water, carrying with it whatever steam or moisture is there generated; the air being by this process rendered wholesome, passes round the edge of the plate, and out at the damper on the top into the apartment. No inconvenience is felt from the burnt air, which is suffered to escape through perforations in the upper part

POISONS IN CHEMISTS' SHOPS. Sir,-Of whatever trade or profession your correspondent Mr. Good, of Brighton, is, or has been, I am quite certain from the tenor of his letter which appeared in your last No. of the Mechanics' Magazine, that he has not been used to a chemist's shop: if he had, he would not propose that " poisons be kept under lock and key." If such plan was to be adopted, particularly that of having "Poison!" written on the door of the cupboard, we shonld soon lose our customers. Mr. Good does not know I think, that in the greater part of prescriptions which are brought to our shops to be made up, poison of some kind or other is ordered, such as laudanum, prussic acid, and many other kinds, to get at which the cupboard would have to be unlocked, and the person waiting for his recipe to be dispensed, would therefore very naturally suppose we intended to poison him, when he saw in very large letters" the word poison on the door.

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It is not every one who knows, that all medicines are poisonous if taken in sufficient quantities; and if Mr. Good's suggestion were to be acted upon, there would be comparatively few things in a druggist's shop, but what would be under lock and key-a shop fitted up in this style would very soon have to be locked up altogether.

Your correspondent must also look at the great inconvenience his plan would subject us to; for example-that of unlocking the poisonous cupboard perhaps fifty, times a day to get at such common articles as verdigris, blue and white vitriol, sugar of lead, spirits of salts, &c., which he perhaps knows to be strong poisons and must be kept locked up.

H. G. says oxalic acid is sometimes taken in mistake for epsom salts, their crystals being like to one another; perhaps if the following simple test for distinguishing them was more generally known it would prevent at least any accident from occurring through their being taken in mistake:-Test-to the suspected article add a few drops of common black writing ink-if its colour remains, it is epsom salts-but if the ink in a short time turns red it is oxalic acid. This is a very easy manner of telling one from the other, and should one life be saved by its being more generally known by means of this letter, I shall be more than repaid for any critical remarks which this my very imperfect attempt at letter writing may bring forth from any of your correspondents. I am, Sir, &c. A DRUGGIST.

STEAM CARRIAGES ON COMMON ROADS.

A new company has just been started, having for its object, the not very new one of introducing "steam carriages and waggons" into general use on common roads. The company state that they have secured the right to the exercise of a patent boiler and machinery, invented by Sir James C. Anderson, Bart.," after many years of study and research, and which are said to combine every requisite for the successful prosecution of the scheme. According to the prospectus, Sir James Anderson has succeeded in constructing a boiler capable of producing the "most dense" kind of steam, and at the same time of resisting any degree of pressure. From this specimen, it will be perceived that the concocters of the company have no very clear ideas of the matter they have taken in hand, and are even ignorant of the very simplest and best-known qualities of the powerful agent they intend to call into their service. As to the flourishes they indulge in with regard to the wonders of the Baronet's invention (and we perceive he is one of the directors into the bargain) they might as well be spared until a little experience has been had; and references to the opinion of the Parliamentary Committee of 1831, in proof of the practicability and economy of common road steam travelling, are worse than useless. The seven years

that have since elapsed, without any progress being made towards the state of things which the report of the committee gravely announced as close at hand, speak volumes on the reliance to be placed on their judgment. The prospectus talks of conveying goods and passengers at double the speed of horse coaches, and at one-half the expense. Let but one-half of this be actually accomplished, and there will be no necessity to raise the ghost of the committee's unlucky dictum, in order to direct the public attention to the desirableness of investing a spare half-million in a common-road-locomotive company.

THE

SUPPLY TO HIGH-PRESSURE BOILERS -SIMPLE WATER-GAUGE BLOWING-FAN.

Sir,-A method of supplying water to a high-pressure boiler appearing to be still a desideratum, the following results of a few experiments directed to that object, may, perhaps, be not unworthy of consideration; although my situation prevents my having much contact with the mechanical world, and other circumstances confine my mechanical operations to a very small scale. The ingenious contrivance of Mr. Baddeley (page 276, vol. xxi. of your Magazine) suggested to me a more easy construction with the same principle, which is represented in the accompanying figure, and which I have had in operation for nearly a twelvemonth.

AB represents the top surface of the boiler; W R the water-line; CE crosssection of two cocks having the water"transferrer" between them: the cock E is of the ordinary construction, that at C differing from it only by having a small hole drilled in its side so as to reach into the main passage of the plug; so that the pipe CQ being soldered to this new orifice, the cock has three ways, any two of which may be made to communicate, while the third is shut off: viz. one to a pipe K leading to an open reservoir of water; another into the transferrer, and a third to the branchpipe CQ, which pipe descends into the boiler so far as to be just above the highest limit of the water-line. The cock E connects the transferrer with a pipe P, which descends nearly to the bottom (or flue-pipe) of the boiler. The two cocks may be supposed to have their handles connected by a bar so as to move simultaneously, so that the passages may either be in the relative positions denoted in the figure, or those obtained by turning both of them a quarter of a revolution to the left; in which latter case, it will be seen that every passage will be closed except from K to the transferrer which is full of steam, immediately to be condensed and replaced by water from the reservoir. On account of the vacuum thus formed in the transferrer, there will be no necessity (as supposed by Mr. Baddeley) for placing the reservoir above the water-line of the boiler, as the water will be raised by atmospheric pressure from a depth depending on the density of the steam, which, if it be considerable, will fill, and form a vacuum in a proportionate length of pipe from the reservoir to K. When the passages are in the positions represented in the figure, it is clear that the water will fall by its own gravity through the cock E into the boiler; the upward pressure of the steam being counterbalanced by the downward pressure of that admitted from the pipe QC. But when, from a frequent repetition of this action, the water-line has reached the pipe Q, the arrangement of pipes and vessel Q CP, forms a continuous syphon, having two legs of equal altitude and pressure, from which no water can flow, and the supply consequently ceases until the waterline again descends below the pipe Q. Much more neat and compact arrange

ments than that in the figure may be easily imagined, as well as the substitution of any description of valves for the cocks; but this represents the one I have experimented with, as it appeared to admit of the readiest and most economical construction. It was found best in practice to make the transferrer of rather large dimensions (containing about a fiftieth of the whole contents of the boiler) and to suffer the water to flow in slowly by opening the cock E to a small extent; and by a due regulation of the aperture, the strength of the steam, always under perfect controul, so as to prevent the waste of much of the heat by the safety-valve. However, the result of my experience was to regard this apparatus, not as a substitute for the forcing-pump, but as a very useful auxiliary to it, in cases of intermission of the working of the engine, or a surplus quantity of steam: and this circumstance will allow the forcing-pump to be of much smaller capacity than it usually is, so that the power required to work it may no longer be an object of consideration; and, accordingly, in one that I made conformably with this view, the loss of force was quite imperceptible.

It afterwards became an object to render the force-pump less liable to disorder than it usually is, and also to provide a test of its efficiency, which I found to be best accomplished by the following contrivance-Let a stop-cock intervene be. tween the force-pump and the boiler with a hole drilled in its side as above described; so that at any time the water which the pump is delivering may be shut off from the boiler and discharged into the open air; by which the quantity injected at each stroke is immediately seen, and any defective action of the valves at once detected. As long as there is no intermission in the working of the engine, and the water is obtained in a moderately clean state, there is no cause to apprehend any derangement or "choaking" of the pump; but as soon as the engine is stopped, the mud and other foreign matter deposited in the boiler, being no longer resisted by the flow of water through the supply tube, finds its way.to the valves of the pump which thus frequently become choaked; on which account it is advisable to close the stop-cock just mentioned, whenever the engine is stopped.

I now come to consider the waterguage, which I have used for nearly three years with perfect success. To the right of the boiler-feeder in the above figure is represented a very slender pipe furnished with a stop-cock, and passing into the boiler through a stuffing-box, S. At M is a ring of metal encircling the pipe, and soldered to it at such a place, that when the pipe is thrust down so as to touch the bottom (or flue) of the boiler, the ring may may rest upon the stuffing-box, S. Thus, the ring M will serve as an index to denote the distance of the bottom of the pipe from that of the boiler. Now to ascertain the depth

of the water above the bottom or flue of the boiler, let the pipe be drawn up through the stuffing-box as far as its length will permit; open the stop-cock and a small jet of steam will flow out; and now let the pipe be gradually pushed down through the stuffing-box until water flows from it, indicating that it has just reached the water-line in the boiler; close the stop-cock, and the distance, MS, will plainly be equal to the depth of water required.

I have read with great pleasure Dr. Ure's theory of the blowing-fan (vol. xxvii, p. 25, Mechanics' Magazine), the importance of which appears to be very generally acknowledged by its extensive adoption in foundries and other establishments; but the conciseness with which this is stated, together with some typographical errors, will, I apprehend, render the calculation unintelligible to the majority of your readers.

This, together with the presumed usefulness of a practical rule for determining the power requisite to drive a given fan with a given velocity, is my apology for offering the calculations in the following form :

If a fluid be made to issue from an aperture with an uniform velocity, by the action of any mechanical power, this ac tion may be obviously regarded as equivalent to that of a similar stream of the fluid issuing from an orifice at the bottom of a reservoir kept filled to a constant altitude, which altitude is proved by all hydrodynamical writers to be equal to that through which any heavy body must fall to acquire the velocity which each particle of the fluid has

In page 25, lines 11 and 20 from the bottom, for read x; line 20 for "be square feet" read "be 2 square feet"; line 22, for "8c read 80."