WORKING STEAM TWICE. meets with the approbation of the military institutions at Woolwich or Chatham (I forget which), it is to be immediately recommended to the adoption of the army. The inventor is a Mr. Downing, a Lieutenant in the Navy, residing at the town of Bideford, in Devonshire. He first invented it for his own private shooting, but, having shown it to some friends, they were so struck with it, that, by their recommendation, he went to London, and is now taking out a patent for the same. I have not seen the gun, nor will the inventor (now) let any body see it ; suffice it to say, that he has made a fowlingpiece weighing altogether but three pounds and a half, and a soldier's musket weighing only seven pounds. There is no wood used in the construction of any part of the gun, not even the stock, which, from what I can collect from the information of the inventor himself, is made entirely of iron. The stock is a skeleton one : the lock of the gun is in the centre of that part of the stock next the barrel: the cock or hammer of the gun is calculated both for the flint and detonating systems, or both of those methods can, by the simplest means, be used at one time, the says, 243 weigh only seven pounds. The in- Your obedient servant, WORKING STEAM TWICE. SIR,I have had various disthe principle of Wolf and Edwards' putes with my fellow-workmen on steam-engine, in which the steam is worked twice over, first at high and then at low pressure. Now I wish to be informed (and I hope the first engineers in the country will not the inquiry) how the steam, after deny their assistance in answering leaving the high pressure cylinder, gains its power to act on the low pressure one? Will not the steam, hammer descending and letting off the gun with flint, and steel, and detonating powder, at the same instant. Copper caps are not used. The in- leaving the high pressure cylinder, have as much power to resist the ventor that the guard of the return of the high pressure piston gun-lock is at the same time its main spring. The gun is water-proofas it will to give action to the low the inventor has loaded it, put it in pressure piston? If so, its double water for a day, taken it out, and action is certainly of no use; to me fired it off as well as if he had only right, how strange it is that men of it has always appeared so. If I am loaded it the minute before. The acknowledged talent should be found gun may be either single, double, or treble barrelled, or even four-bar- putting upon the world so complirelled, which four barrels are all let machine! How, I will ask, is it cated, so expensive, so delusive a off with the same lock without any extra trouble, and, if required, all possible, after working the high at the same moment, or regularly pressure cylinder to the full extent one after the other. The bottom of of the pressure of steam in the the barrel, near the touch-hole, is boiler, to gain another ounce of bored conically, so that the point of the cone is the touch-hole. I believe a soldier's musket is generally about fourteen pounds weight: the inventor will take a musket-barrel, and finish it after his new invention, and the gun shall, when complete, Westminster-bridge-road, power? I am, Sir, F. JK N. No. 5, Mason-street, "The mischief that has happened in coal mines, in consequence of the explosion of inflammable air, has sometimes been of so destructive a nature, as deeply to interest the feelings of every benevolent mind. Reflecting upon this deplorable subject, and considering, that whoever can point out a method of mitigating the power of foul air, so as to prevent the recurrence of such disasters in future, will be entitled to the thanks of his fellow-creatures-it appears to me, on deliberating this most momentous subject in my mind with attention, that there is a probability of effecting so desirable an object by means of irrigation. "It is well known, that when a deep well has long been closed, and it is intended that it shall be cleaned out, or repaired, it is customary with those who are aware of the bad effects of the deleterious vapours that may be found at the bottom to throw down a quantity of water; after which a labourer may descend to his work with safety. "Upon this principle, I am of opinion that the foul air of coal or other mines may be deprived of its power of explosion, by a similar process, in attending to the following hints. "I would recommend a fire-engine, capable of being worked by four or six men, to be used where the foul air is perceived, and another person to point the pipe. This engine should be built upon four wheels, for the more easy conveyance of it from place to place. When at work, I think the director of the pipe should chiefly aim at the roof of the mine, and endeavour to cause the water to fall down, as much resembling a shower-bath as he can. Supposing the pipe is furnished at the end with a perforated nozzle, like that of a common watering-pan, it will, perhaps, answer that end better. "A large portion of the mine may be thus watered in a few hours, and I presume the air contained therein will be found much purified by it, the danger of explosion prevented, and be the happy means of saving a number of valuable lives. "As it possible a sufficient quantity of water may not every where be procured, it may be let down from above, in the nearest shaft, and from thence conveyed to the engine. "This operation, performed as often as may be thought necessary, I trust, will render those dark abodes much less destructive to human life than they are at present. "As a corroboration of my system succeeding, when put in practice, I am informed by those who have explored the mines in question, that the foul air is never observed to generate under porous roofs, or where the water falls down in continual drops. "Another, and probably a more effectual method of expelling foul air, or at least of rendering it less obnoxious to the workmen, may be by ventilation, i. e. by forcing down a quantity of atmospheric air to the bottom of the pit, by means of a powerful cylinder-bellows, through a tube of iron, and from thence conveyed, by a leathern hose, to any part where the air is inflammable. "It seems to me not altogether impossible, that the very same engine which draws water out of the pit, may be so contrived as to be occasionally applied to the purpose of ventilating the coal-works below. "If a trial of only one of the abovementioned methods should be thought insufficient for the purpose, I apprehend the operation of them both, either alternately or at the same time, will render that destructive air very inoffensive. "As I consider the coal trade, in every point of view, of very great national importance, I have therefore presumed, in few words, to offer some hints upon the means of procuring that fuel in the pits with safety to the colliers; and should they be thought worthy of trial, and found to answer my expectations, in rendering the air confined in those mines less pernicious than they have hitherto been, I shall be happy on reflecting that I have, in some measure, promoted the public good as well as benefitted the cause of humanity. "JOSEPH SENHOUSE. Whitehaven, May 15th, 1810." Sir Joseph Banks, then President of the Royal Society, informed me, afterwards, that my hints were favourably received by the Members of that Board; and, as to himself, that he so far approved of my ideas, that he would certainly have a trial made if he had any mine infected with foul air.-J. S. PYROMETER. Mr. Macome, in his Lecture on Caloric, to the Johnstone Mechanics' Institution, observed that, several LIGHT, HEAT, ELECTRICITY, AND MAGNETISM. years ago, when steam was first in- DIFFERENCE IN THE APPEARANCE SIR,-Sitting, a few days ago, with a party, enjoying the delicious and forbidden fry at the Ship at Greenwich, the conversation turned upon the cause of an appearance 245 of saccharine matter per quarter? I have, for the last three years, had frequent opportunities of noticing the extract, per quarter, from different parcels of inalt, but have not met with any that would produce half that quantity. I am, Sir, Your obedient servant, P.S. I have been rather surprised that some of your intelligent Correspondents have not given some instructions on the art of brewing. I am confident, if some practical brewer would let the public benefit by his experience, by pointing out the temperature of the water for a first, second, and third mash-the length of time for boiling-and, what I conceive to be more difficult than any other part of the process, the fermentation of the worts, &c. it would be very acceptable to the generality of your readers. MAGNETISM. which had been constantly remarked LIGHT, HEAT, ELECTRICITY, AND there, namely, that whenever it was high water, objects on the Isle of Dogs, whether animal or fixed, appeared to exhibit more of their parts in height and more brilliantly than the same objects did when viewed at low water. Much variety in opinion was produced, but nothing satisfactory. Can any of your Correspond ents favour us with a solution of what is presumed to be an optical illusion? I remain, Sir, June, 1825. BREWING. SIR,-I shall be greatly obliged if your Correspondent, JJ, (vol. iv. page 144) will let me know, through the medium of your valuable miscellany, where malt may be purchased that will yield 200 pounds SIR, The polite reception given to former communications, encourages me to venture again to address you, and I feel much pleasure in adding my mite towards your laudable endeavours to extend scientific information to the humbler classes of society. The following facts are very important in their utility, and tend to show the analogies of light, caloric (or heat), electricity, and magnetism, and I hope are, in some points, original. My object will be to prove, that light is a substance, and the phenomena of caloric (or heat), elec⚫tricity, and magnetism, are modes of that substance. It is, I am aware, a venturous effort to overthrow the theory of a Davy and a Wollaston, both of whom have stated their opinion, that light and heat are not material; as also, by inference, electricity and magnetism. It will not be in my power to convey my argu 246 LIGHT, HEAT, ELECTRICITY, AND MAGNETISM. ments in one communication; I shall, therefore, from time to time, resume the subject, and I invite candid criticism with a view to my correction. I shall give, in a tabular form, some, among numerous other, analogies of light, &c. and I hope this arrangement will place the subject Light. Emanates from the sun...... in a clearer view, and will be better retained in the mind. When we consider the vast operations which light and heat are continually effecting in the animal, vegetable, and mineral kingdoms, any ideas, even though founded in error, will tend to sharpen the edge of inquiry respecting these agents. Travels with great velocity.. Ditto Penetrates certain hard bodies.... Ditto Imponderable, or does not give weight to bodies Produced by friction Ditto Ditto Ditto .... Transmitted in straight lines Ditto Produced by percussion Ditto LIGHT, HEAT, ELECTRICITY, AND MAGNETISM. I do not pretend to have given all the analogies of light, &c. but here are quite enough to warrant the idea of identity; and I do not think it impossible to prove, that all the phenomena of nature are absolutely governed and directed by light, acting in its various capacity of heat, electricity, and magnetism. The very operations of animal and vegetable sensation appear to depend upon these principles, and cannot be explained in the absence of them, as we cannot form any idea, not even an abstract one, of sensation without its cause; and it may simply be stated, for example, with regard to vision-that, do away with light, or do away with eyes (or the sense of sight), and the consequences are the same-the one necessarily depends on the other. Light and heat have been considered as motion by many respecta ble philosophers; but it is yet to be explained how it can act, if only vibration, upon the senses of animals, upon animal organs. The sense of touch, which pervades the whole surface, and the interior of animals, or, in fact, wherever there are nerves, cannot be excited, even in the most irritable nervous arrangement, without the actual contact of a material agent (leaving out, for a moment, light, heat, electricity, and magnetism, which are called imponderable bodies). We are susceptible of rough and smooth, soft and hard, round and angular, cold and hot, dry and wet, heavy and light, greasy and sticky, fluid and solid, &c.; but all these varied sensations of the nerves are inseparably connected with parts or combinations of matter; and no sensation is experienced where matter can be denied to be present. The two senses that next depend upon material agency, are those of smell and taste. Hence it is obvious, that their most universal action depends entirely upon the contact of a particular set of nerves, and a particular exciting class of substances. Hearing is produced by vibration or motion; but since it is proved that the auditory nerve would be inoperative in a perfect vacuum, it is hardly necessary to repeat the known 247 fact, that it is the pulsation of the air, acting on an organ and nerve, of such intense and delicate acuteness, which produces sound. Now, if the vibration of a fluid so fine as air, and which is agitated by the falling of a pin, or the hum of a gnat, be enough to stimulate the auditory nerve, it is not difficult to imagine a matter, yet finer (such as light may be supposed to be), acting on an organ of infinitely fine construction; and the difficulty is to get over the fact, that all the other senses depend entirely upon material agents, and yet that vision does not; for if light is mere motion, it is nothing; that is to say, it is not matter. It is not possible to imagine a nerve to be acted upon by mere motion, or the vibrations of motion; it is absurd and most unphilosophical. The image (or reflected rays of light transmitted from the object viewed) painted on the retina is a real material painting, which acts by vibration on the optic nerve, and it exercises all the properties of material agents, it tires the nerve, and if too long applied, would injure, and eventually destroy its irritability, upon which its function depends. A strong flash of light is as painful to the eye as a smart blow is to the body; the continued action of light, or of any strong object, to the eye, is as injurious and painful as longcontinued pressure is to any part of the body. Light has been thought to consist of particles of a certain magnitude; heat, of particles larger; electricity, larger than those of heat; and magnetic particles, of the largest of all, and hence are more confinable than the other three. This opinion harmonizes with the laws of atomic arrangement; and it is easy to conceive the condensation of one, two, three, or four atoms of light, which would produce, so combined, very different degrees of effect, as we see in other forms of matter in chemical arrangements and affinities. The size of the particles of light may be inferred from those of air, by the difference between the velocity of sound and light; for light to vision bears the same analogy as vibrations of |