ter that, the retort A3 is charged; in one hour and a half more the retort A1 is ready to be recharged; the coal having undergone the usual process of six hours subjection to the heat of the furnace; and so on in succession alternately, each retort being submitted to the action of the fire for the same time. In the retort A1 (supposing the operation to be in full action,) the first hour and a half or quarter time of the charge, the dense volatile matter and ammoniacal water of the coal is set free, and passes into the retorts A2 and A3, where, in connection with the carburetted hydrogen which A3 is producing, and the sulphuretted and carburetted hydogen which A3 is producing, it is further distilled. Each retort will thus in succession be performing the stage of operation here represented. Previously to a retort being charged, its communication with the other, and with the main G must be cut off, by the valves C and H; and one retort only-that is to say, the one of the three (or any other series used) which has been longest subjected to the action of the heat, must communicate with the main. The figures are but roughly drawn, and all the parts except those relating to my improvement, are in skeleton. The exterior dotted lines represent the outline of the brick setting of the retort bed. Should you think this invention of mine of sufficient importance for publication, I shall be happy to send you descriptions of other contrivances relating to the same subject, which I have at various times made, experimented upon and worked. Brighton, November 15, 1839. I am your obedient servant, Economical Portable Hot Bath. WM. BARNETT. Sir,-The following novel plan of heating a bath was communicated to me by Mr. Le Croix, of Upper Norton street, New Road, Regent's Park, whose idea it is; and thinking from its simplicity, it deserved being made public, I respectfully offer it for insertion in your valuable pages, if you think the plan merits a place in them. In any room with a grate c, a fire is to be made, the bath a filled and wheeled towards it, being fitted on large castors d to move readily; the tube b attached to the bath, which is adjusted to the height of the bars is then inserted between them; in a short time the water will be heated to the degree required, when it may be wheeled to any part of the room without the Teast annoyance. G. M. BRAITHWAITE.* Ibid. * We should be glad to receive from the readers of our Journal an account of any mode of heating a movable bath, which they may think preferrable to the foregoing. G. Progress of Physical Science. Experiments to determine the Fluency or Viscidity of Different Liquids at the same Temperature, and of the same Liquids at different Temperatures. By Dr. Ure. Having been employed professionally, Dr. Ure observed, to investigate the operation and merits of a new lamp, recently patented by Mr. Parker, in which the oil is heated by the flame of the lamp to the temperature of from 200° to 250°, before arriving at the wick, it was desirable to determine the degree of fluency imparted to oils by a certain elevation of temperature. The light emitted by this lamp, when supplied with the viscid, and very cheap, but nearly scentless, southern whale oil, surpasses in purity and whiteness the light of the best mechanical lamp, though it be fed with the best vegetable or even sperm oil. This superiority is in part due to the form of the chimney, and to the oil being maintained uniformly at the level of the bottom of the frame; but it must also be ascribed, in a certain measure, to the high temperature and fluency of the oil, by which it enters more readily into complete combustion, than cold and viscid oil could possibly do. The preparatory heating seems to act on the same principle here, as it does in the smelting of iron by the hot blast. Having presented a memoir upon the subject of the lamp to the Society of Civil Engineers, which will appear in their transactions, I shall decline entering at present further into its merits. In that memoir, I stated the results of some experiments which I had then made upon the fluency of liquids, by means of an apparatus, consisting of a small glass syphon, and a platina capsule, containing a measured quantity of the liquid to be run off through the syphon. Having since had reason to imagine that certain numerical errors had been occasioned by variations in the position of the syphon, though the general results are true, I have recently repeated the experiments with another form of apparatus free from that fallacy, and submit the following brief account of them. Upon this occasion I put the liquid, either cold or heated to a certain temperature, into a glass funnel, terminated at its beak with a glass tube of uniform bore, about one-eighth of an inch in diameter, and three inches long. The funnel was supported in a chemical stand, and discharged its contents, on withdrawing a wooden pin from the beak, into a glass goblet placed beneath, alongside of which a chronometer was placed to indicate, in seconds, the time of efflux. The volume of liquid used in each case was the same,—viz. 2,000 grain measure, at 65° Fahr. The times of efflux with liquids of the same specific gravity and bulk, in the same vessel, vary with the viscidity of the liquids, and serve to measure it. A correction ought to be introduced in estimating the times of efflux of hot liquids, on account of the enlargement, by expansion, of the bore of the glass tube; but this, being a point of little consequence in the practical application of this inquiry, has been neglected. When the funnel and glass tube were faintly smeared with oil, though per fectly pervious, and apparently clean, boiling hot water having been run through them: So great is the repulsive influence between oil and water, in retarding the flow of the latter through a small orifice. The rape-seed oil is so viscid, as to burn with difficulty in lamps of the ordinary construction, but in the hot oil lamp of Parker it affords a very vivid light. In my former apparatus, the difference of level between the two legs of the syphon, which constituted the effective pressure of efflux, was only half an inch, whereby 2,000 grain measures of sperm oil, at 64°, took no less than 2,700 seconds to run off, while that volume of oil of tur pentine ran off in 95 seconds. It would, therefore, appear that the fluency of a viscid oil diminishes in a very rapid ratio with the diminution of pressure. Hence, an oil will burn well in a mechanical lamp, where it is raised to the level of the bottom of the flame by pump work, which will afford a very indifferent light in one of the French Annular or Sinumbral lamps, where the supply is given by a very slight pressure. Prof. Forbes asked what was the diameter of the orifice of the funnel through which the fluids ran, and what was the quantity of each fluid experimented upon.-Dr. Ure said, that the orifice had a diameter of oneeighth of an inch, and the quantity of each fluid used was 2,000 grains.Prof. Forbes said, that the interest he felt in these experiments arose from the great importance, in some of the researches he was engaged in, of sustaining the action of the lamp in an unchanged state during the progress of an experiment, and sometimes during a series of experiments; but the changes to which even the best ordinary lamp was subject were so anomalous, and the causes so beyond the reach of discovery, as to be quite disheartening. The instrument that he used for measuring minute changes of temperature was so delicate, that the heat given out by even an apparently well-burning lamp, often appeared to be in a constant state of change, the needle indicating it by an almost constant oscillating motion of even several degrees; even lamps, whose wicks were made with the greatest care, were subject to these changes; and the only wicks which he had found to furnish a sufficiently steady temperature for his purposes, were those made by Locatelli, of Paris. Athenæum. Proceedings of the British Association. Divisibility of Matter. The President said, that as one or two papers had been withdrawn, he would proceed to make some remarks on Dr. Wollaston's argument respecting the infinite divisibility of matter, drawn from the finite extent of the atmosphere. He observed, that Dr. Wollaston had proceeded on this supposition; that if the extent of the earth's atmosphere be finite, air must consist of indivisible atoms; since, as he assumed, the only way in which we can conceive an upper surface of the atmosphere is, by conceiving an upper stratum of atoms, the weight of which, acting downwards, is balanced by the repulsive force of the inferior strata acting upwards.-Mr. Whewell maintained, that such a mode of conception was altogether arbitrary, and the argument founded upon it quite baseless; for if we investigate the relation between the height of any point in the atmosphere, and the density of the air at that point, upon the supposition that the compressing force is as the nth power of the density, we find that the density vanishes at a finite height whenever n is greater than unity. Therefore, though the atmosphere do not consist of indivisible particles, it will still have a finite surface. In fact, the finite surface of the atmosphere no more proves the atomic constitution of air, than the finite surface of water, in a vessel, proves the atomic constitution of water. But it will still be asked, how then is the highest stratum of air supported? To which the answer is, that there is no highest stratum of definite thickness. Supposing the atmosphere finite, every upper stratum of air bounded by the upper surface of the atmosphere, has the upper part of that stratum supported by the lower; and, however thin it be, it has still an upper and a lower part which have this relation to each other. The question, What supports the uppermost stratum of the atmosphere? is of the same kind as the question formerly discussed by writers on mechanics: What is the velocity with which a body begins to fall? Professor Stevelly said that perhaps this question would be more familiar to many persons if the scientific language of the President were made more popular, by explaining, that the real question was, whether matter was so constituted as to be infinitely divisible? or consisted of molecules or atoms, which could not be farther divided, de facto at least; for in imagination any portion of extension, however small, can be farther subdivided. This latter, Wollaston produced strong probable reasons for considering as the true statement; his argument from astronomy was, that if matter were capable of indefinite subdivision, the atmosphere would be indefinitely extended, and then the moon and planets would, each, in the lapse of time, have collected atmospheres from ours, bearing to one another the proportions of their power of attraction; this was not the case, as astronomy proved: for instance, the density of the atmosphere of the moon was not the 2000th part of that of the earth, at their respective surfaces. The earth's atmosphere then did not even extend, in space, as far as the moon.-Dr. Daubeny said he was sorry to find, that the doctrine of atoms, which on chemical grounds, he considered as probable, had been deprived, by the President, of the support which the memoir of Dr. Wollaston had seemed to afford it. He had been disposed to think more favourable of that argument, from finding that M. Dumas had resorted to a very paradoxical supposition in order to reconcile the conclusions of Wollaston, which he admitted, with the doctrine of the infinite divisibility of matter, which he also maintained. M. Dumas, in his work Sur la Philosophie chimique,' maintains, that a limit VOL XXV.-No. 2.-FEBRUARY, 1840 12 would be assigned to the extent of our atmosphere in consequence, merely, of the extreme cold of the upper regions, by which the air would be condensed into a solid form. Hence, according to him, the boundary of the atmosphere would consists of a sort of crystalline sphere, such as what the ancients had imagined, but with this difference, that the celestial luminaries according to Dumas's views would lie beyond the sphere, whereas Ptolemy supposed them to be included within it. Leaving it for opticians to decide how far such a palpable medium could interfere with the transmission of light and heat from without, Dr. Daubeny contended, that the temperature which Fourier had assigned to the celestial spaces was too high to allow of the solidification of oxygen and nitrogen gases, which indeed had been found to resist a degree of artificial cold greatly inferior to this, as, for instance, that produced by solid carbonic acid. But though he could not agree with Dumas in this particular point, he was quite ready to bear his testimony to the general merits of his work, and in particular, to point out the satisfactory manner in which he has shown, that matter cannot be separated into its ultimate particles, either by physical or by chemical means; but that elastic bodies consist of groups of atoms mutually repulsive, and that chemical combination takes place between smaller groups indeed of the same, but not be. tween individual atoms. Ibid. On the Crystallization of Carburets. By S. BROWN, M. D. The object was to lay down a new form of the maxim of crystallization -viz. That when the particles of a solid body are slowly evolved from the decomposition of a substance of which it, or its elements, are chemical constituents, they cohere in crystals, and that independently both of the fusion (or solution) of the body crystallized, and of the presence of any fluid medium or molecular motion whatsoever. This principle the author deduces from a multitude of experiments. The principle is applicable to substances which are infusible and insoluble; and, indeed, as the title of the paper imports, has been inferred from observations made on such substances-viz. the metallic carburets, as produced by the decomposition of sulphocyanides and cyanides. The subjects of the experiments were the carburets of iron, copper, zinc, lead, tin, manganese, &c. These carburets are, in their amorphous form, dark and opaque, being not easily distinguishable from charcoal. By the use of the following formula, the author prepares these substances in transparent, colourless, and intensly hard little crystals. Formula:-Let a parcel of any cyanide or sulphocyanide be decomposed by heat, in exclusion from air, at that point of temperature which may be called its point of decomposition, and the resulting carburet is found to be of crystalline structure. It is a tedious process, requiring five hours for a drachm of cyanide of zinc. The author exhibited specimens of crystals procured in this way, especially of carburets of iron, which cut glass. The application of these facts and their principle to the explanation of certain mineralogical and geological cases of crystallization, as well as to the arts, the author left with the Section; but called attention to that point of view in which his labours are chiefly valuable; that they prove that the only essential condition of the crystallization of a body is, that its particles be slowly segegrated from any previous condition whatever. In conclusion, he observed that the chemical identity of carbon and the diamond has been long established by inference. Now, there is as great a difference,-nay, exactly the same difference, between the |