ment? Luckily, Dr. Dalton's theory thus explains this apparent anomaly, according to Mr. Armstrong's new version; for he would prove, that the smoke and unconsumed combustible gases, after having passed round the boiler, and being intermingled and diffused, under the Daltonian theory, are, by the magic peculiarity of a fan, and at the very same time, separated, (as chaff is from wheat,) the useless and incombustible gases alone passing up the chimney, while the combustible portion, thus miraculously separated under this diffuso-separative process, returns again, (under said squirrel system,) to the ash-pit, furnace, flues, and boiler. Thus we find that Dr. Dalton's theory of the intimate intermixture and diffusion of gaseous bodies without reference to their respective specific gravities, (long since admitted to be correct by the whole chemical world,) is now, by the new light chemistry of Mr. Armstrong, discovered to possess the additional peculiarity of separating the combustible from the incombustible gases, just at the moment when, by the same laws, they had become intimately diffused among each other. To this, however, must be added the peculiar action of a fan, which, also acting in a double capacity, propels the useless gases up the chimney, and sends the useful ones round again to the furnace! Who will hereafter despair of impossibilities?

Mr. A. observes, “ your chemical readers" (doubtless he thought it was too profound for mechanical ones,) "will be aware that this circulatory process cannot go on without atmospheric air, and which air is admitted by a small aperture between the fan and the smokeflue." How this small aperture can admit 360,000 cubic feet of air for each ton of coals, the theory sayeth not.

Mr. A. observes, "It was demonstrated by Dr. Dalton, that different gases act as vacua to each other, while Professor Graham has shown that the different gases have a tendency to diffuse into each other with different degrees of rapidity, which bears a certain relation to their specific gravity; and hence he, (Professor Graham,) shows that, by availing ourselves of this tendency in mixed gases, a sort of mechanical separation of the various gases may be effected." Here is a flight of philosophic ingenuity, with a vengeance! What will

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Professor Graham say of this "mechanical separation," thus attributed to his idea of the "tendency of gases to diffuse into each other?"

But, lest any doubt should remain on the subject, we are told in plain English, "it is precisely this separation," (after the previous diffusion,) "that is effected by Mr. Cheetham's process." How far Mr. C. may feel obliged to his eulogist, for this explanation of the process, I leave to him to say.

Now, the ingenuity of this philosophical diffusion-separation process reminds one strongly of the philosopher, (Swift's, I believe,) who suggested an equally ingenious mode of producing a diffusion of talent and temperament in the human species. His plan was, the taking a slice off the brain of the sanguine man, and exchanging it for a slice from the brain of the phlegmatic-thus virtually reconciling diffusion with separation. Equally ingenious, and equally practicable and valuable, is this with Mr. Armstrong's separation-diffusion theory. (To be concluded in our next.)

PECULIAR CASE OF OXYDATION.

Sir, Will you permit me, through your pages, to ask advice of some of your readers under the following circum

stances:

I have a carpenter's stove for steaming plank in, which, when fully exposed to the atmosphere, I found the steam to condense so rapidly, as very much to lessen its utility. To counteract the speedy cooling I had it cased with plank on the outside of the flanges, by which its separate pieces are secured together, and the space between, say 2 inches, filled with sawdust: this effectually prevented condensation, and, as I fancied, answered my purpose; but on renewing a part of the casing after six months use, I found the stove rusted th, or upwards, of an inch, and the decay apparently going on. Now, at this rate, it will very soon be holed through, and if some of your correspondents would, through the Mechanics' Magazine, favour me with advice, they would much oblige,

Your obedient servant,

A CONSTANT READER.
Glasgow, January 13, 1842.

the patent, from 1827 to 1841. Many of them are now in use, in various parts of England, and can be produced to vouch for themselves. Besides what has been stated, there is that which will, no doubt, be considered rather a peculiar feature in the case. Some hundreds of these lamps were made, in virtue of Upton and Roberts's patent, by Messrs. Timothy Smith and Sons, under the superintendence of Mr. Jeremiah Bynner, who was then acting as the foreman of Messrs. Smith's Lamp Factory, and this was at least two years before he obtained his patent. This is rather a startling fact, and will surprise those who know what has to be done to obtain a patent, whether told in your pages, or reserved for a court of law.

What I have here stated, Sir, are facts, which I am prepared to substantiate; they are facts which concern the public, and give the free and immediate use of these caps or deflectors to every one. If Messrs. Smith are desirous of making a statement, let them make one which will meet the point at issue. If actions at law are cited, let them be decided ones. The public are not, they may rest assured, to be hoodwinked by reference to an undecided action, which proves nothing, and may end, as such affairs not unfrequently do, in stripping a doughty assailant, like the ass in the fable, of the lion's skin.

I remain, Sir,

Your obedient servant GEORGE UPTON.

Oxydator Office,

33, George-street, Hanover-square. January 11, 1842.

THE LATE MAGNETIC DISTURBANCES.

"In the advance of knowledge, the value of the true part of a theory may much outweigh the accompanying error; and the use of a rule may be little impaired by its want of simplicity. The first steps of our progress do not lose their importance because they are not the last; and the outset of the journey may require no less vigour and activity than its close."-Whewell, Hist. In. sec. i. p. 118.

Sir, The remarkable magnetic disturbance at the Greenwich Observatory had engaged my attention previously to your announcement of it in your last number.

VOL. XXXVI.

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An increased volcanic action, (aurora borealis,) has been occasionally observable at the north pole for a length of time. This has, of course, occasioned a great disruption of ice, and consequent approach of it towards the equator, the evaporation of which has filled the atmosphere with moisture. By the volcanic action of the 25th of September, the overloaded metallic fluids were shaken, and the additional moisture has been coming down ever since, like the dripping of an over-saturated sponge. It is not during the commencement of the derangement of the system that the pulse is the most affected, but at the crisis of the disorder. The liquid that is tranquil in the half-filled cup shakes on the brim. There can be no doubt that the sky, (the upper region of the atmosphere,) is the emporium of metal in a state of sublimation, or of electricity. To this metal moisture adheres. Look at a flake of snow-what else gives it its star-like form, with its serratures ? I know not whether the geologist has ever thought of tracing his metallic veins to the skyif he have not, behold a theory for him, worthy of his deepest consideration. Í have another theory for him, on the subject of coral rocks. All in good time.

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authority from whom the prefixed motto is "In the next place," says the same learned taken, we may venture to say, that advances in knowledge are not commonly made without the previous exercise of some boldness and science in guessing.”—Vol. i. p. 411.

A blunderer is better than one who cannot guess at all, and who rests satisfied with not knowing. I took it into my head, the other day, to place a great U before things unknown. What a number of U's! How many which there is no chance of expunging, while it is believed that matter can continue to move without a continuous force. Great a man as Newton undoubtedly was, "in sweeping the skies," he resembled "Dame Partington," or the silk-merchant who wanted to have all the silk-worms' eggs destroyed, because he found some moths amongst his cocoons. What had a moth's egg to do with silk? I have lately been told, that much of what I have brought forward is not new-that it was known to the ancient pagans. I know that: I know also that it is known to the pagans

F

of 1842. What of that? Do we not eat, drink, and sleep, as the pagans did, and do? Why should we not think as the pagans did, and do, in matters that do not interfere with our faith? It is just as absurd to think people are wrong in all things, as right in all things. The part of my Theory of the Universe which I believe to be new is, that of the absorption of a universal fluid being the cause of the approach of solids to the earth-that the opposing currents of air are the cause of the approach of bodies without absorption-that there is positive cold, consisting of separate atoms, in a peculiar fluidand that positive heat is a globular arrangement of the said atoms with the said fluid, the change being wrought through the medium of vegetable and animal existence, and that the continuane of all motion is due or caused by life. If this has all been made known before, I suppose the objection is also known. What is it?

I pretend to no more than a wish to make others see the beautiful view which I have seen. If any one is afraid of a "chamois-hunt," as Coleridge calls following a deep thinker, he can but turn back. I do not dispute the force of the attraction of a good fire, an easy chair, and a book. Go back. When Socrates was asked what he thought of the theories of Heraclitus? he replied, that "what he understood of them he found so elever, that he concluded what he did not understand was so likewise." There is a precedent for all philosophers. At any rate, he did not condemn what he did not comprehend.

In a former number of your Magazine, my attention was drawn to the subject of the growth of trees. Is it attraction that lifts those enormous masses above the earth? Yes-capillary attraction! What is capillary attraction? Something very different from any account of it that I have as yet seen, or I am much mistaken. Of this at another opportunity.

I remain, Sir, your obliged, &c.,
January 15, 1842-

E. A. M.

Ma. PILBROW'S CONDENSING ENGINE. Sr. As Mr. Pilbrow has invited diseussion on the merits of his condens• Sec Mech. Mag., vol. xxxiv. and XXXV.

ing engine, I beg to offer a few observations on that part of it which appears to me most open to objection.

Mr. P.. I think, overrates, in the first place, the perfectness of his vacuum as compared with that of the common engine. He says, speaking of the condenser of the common engine, that “all air and gas cannot be withdrawn at each stroke of the air-pump; half, at least, must remain in the separate condenser, which will expand and make the extreme vacuum less by lib." One might almost be led from this to suppose, that Mr. P. meant to say that all the air and gas given out in the last condensement cannot be withdrawn at one stroke of the air-pump, but that a portion of it remains to vitiate the vacuum. But what must be the inevitable result, if such were the case? Certainly this, that the air-pump being unable to withdraw all the air and gas given out at each condensement, that portion which is not so withdrawn, or remains behind in the condenser, must continue to accumulate until the vacuum become thoroughly vitiated. Mr. P. must perceive that such must be the result on the supposition stated; but as no such incremental accumulation of gases takes place in the condenser of the common engine, it follows that the airpump does in fact withdraw all the air and gases given out in each condensement. A certain portion of air or gas no doubt always remains in the condenser, arising from the unlimited expansibility of gaseous bodies, and the consequent impossibility of any air-pump, however perfect, completely extracting it from a chamber which its own piston does not fill, and in which, therefore, it will find room to expand. It may, however, be attenuated to a certain point, and there is nothing in theory or practice, except in as far as arises from imperfection in construction, to prevent the air-pump of the common engine maintaining the vacuum at that limit. As the pisten of Mr. P.'s condenser fills or traverses the whole internal space or chamber, it certainly expels every portion of air or gas from within, and his condenser is therefore free from the imperfection just adverted to in the condenser of the common engine; but it does not necessarily follow that in practice he outains a better vacuum than that of the common engine; for there is another consideration to be taken into ac

count, namely, the difference in size or capacity between the two condensers, and whether the vacuum in his comparatively small condenser may not be as much vitiated at the end of each condensement as that of the common condenser, which is not limited in capacity like Mr. P.'s. Take the state of the two condensers at the end of one condensement; and just before the engine makes a new stroke. The vacuum of the common condenser is vitiated by the gases given out during the condensement just concluded, the vapour due to the temperature of the condensements, and that constant portion of gas which the air-pump cannot withdraw; but then these are diffused in a large space or chamber. In Mr. P.'s condenser-the vacuum is vitiated in like manner by the gases given out during the condensement just finished, and by the vapour due to the temperature of the condensements-being free, however, from the constant portion of gas of the common condenser; but then they are cooped up and confined in a small or limited space; and it may be worth inquiring whether, under these circumstances, their elasticity, or power of offering resistance to the piston of the engine, is not as great as in the common condenser, or, in other words, whether in practice his vacuum is at all more perfect than that of the common condenser.

The main objection, however, to Mr. P.'s engine, and which will more than counterbalance any advantages it may have in other respects over the common engine, is, the enormous resistance to which it is subjected, towards the end of each stroke, by the pressure of the atmosphere on such a large surface as the area of the condenser piston-a resistance which, added to the work performing by the engine, may well nigh go to stagger and paralyze its movement.

I am unable to perceive the soundness of Mr. P.'s reasoning on this point. He says, "No enormous burden thrown on my engine, not an ounce, whether the condensement is thrown out by a large area of piston and a short period of discharge, (as in my engine,) or by a small area of piston and a long period of discharge, (as in the present engine,) the total effect of the pressure of the atmosphere must be the same, the quantities being, as they will be, equal." In what respect are the

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quantities equal? The air-pump of the common engine is made of definite proportions, to effect a definite end-the expulsion of the gases and water which are found in the condenser at the end of each condensement; and that proportion is given to it which is just suitable to produce the result intended, and not more. The size of Mr. P.'s air-pump, or the area of his condenser piston, (which is the same thing,) is not made with reference, primarily and only, to the purpose of ejecting the gases and water resulting from each condensement, nor has it those proportions which would be given to it, if it had merely that end to fulfil. I cannot acquiesce in Mr. P.'s reasoning, that a large area of piston and short period of discharge necessarily come to the same thing as a small area and a long period of discharge, which is the inference deducible from his words in the quotation I have given. Enlarging the area of the piston does indeed defer and shorten the period of discharge; but, however much the area may be enlarged, a time must come, though it be at the very end of the stroke, when the condensements must be discharged, and the pressure of the atmosphere let in on the piston yet I can hardly think that Mr. P. will assert that the total amount of pressure on the piston is still the same.

There are two things which, it appears to me, Mr. P. has not satisfactorily proved, and I submit them to his candid consideration.

1. That the total amount of pressure or resistance from the atmosphere on his condenser piston is the same as, or not greater than, the resistance of the same fluid on the piston of the air-pump of the common engine-the steam cylinders of both engines being in all respects alike.

2. Supposing the amount of pressure of the atmosphere to be the same in both, whether the accumulation of this resistance at the end of the stroke, when the crank is in the worst possible position to carry on the movement of the engine, is not far more prejudicial to its effective working, than the same resistance diffused over the whole, or a considerable portion of the stroke.

January, 1842.

N. N. L.