472 



KNO^A^LEDGE 



[Maech 31, 1882. 



now bcfnro mo ton iiUndanI works on rhomi«lry nnd lilowpipo 

 •nnlynix. iii nol oni- of wliicti in tli<- li)fiir<> of thc< pyrocono rorrorlly 

 drnwn ; Imt, «■ it wotilil novordo to tukouptho Bpiicuof Ksowi.KiMiK 

 with otToncou« ilnwinga, I ahnll horo moroly iniiort two j (o) from 



llloxam's Chemistry ; ('■) from Thorpe's. In thcflo pictures it, will 

 ho scon Ihnt the " nozzio " of the blowpipe appears to bo scndinfr a 

 blast into the ceiitre of tho pyrocone, whicli latter is therefore s.'iid 

 hy most chemical writers to bo as hollow as tho luminous llamo of 

 a candle undoubtedly is; a statement which, as shall bo abundantly 

 proved in the course of these " lessons," is also quite incorrect. 



Now, let us light a common candle in daylight, and apply a blow- 

 pipe blast to it, near a window, viewing tho resulting pyrocone by 

 transmitted light (that is, holding tho candle between us and the 

 window) on a level with the eyes; or, speaking concisoly, in tho 



f- / C . ^ . 



horizontal plane of vision. This is something like what wc see, but 

 by slanting tho candle a little, we can see quite distinctly the 

 actual path of the blast on tho u^-p^r surface of the pyrocone ; and 

 moreover, we can easily prove, while holding the candle or lamp 

 upon this level, that it is impossible to force the blast inside of tho 

 pyrocone. Another proof which I take from a former paper (Proc. 

 Roy. Soc, Vol. XX.) is that, in looking directly down (or perpen- 

 dicularly) on n pyrocono formed upon a thick wick, as that of a 



Berzelins' lamp, wo see the black carbonised wick through the 

 Bpace which is always formed in the centre of even.- luminous flame, 

 and not throngh blue fiery matter, as would be the case were tho 

 blast in the centre of the blue pyrocone. Yet another proof lies in 

 tho fact that upwards heat-radiation is almost entirely stopped by 

 the superposed blast. 



Simple learners like the poor workmen to whom I chiefly address 

 these little " lessons " — though I myself have quite as muoh to learn 

 in the matter as to teach — will scarcely credit the fact that none of 

 the eminent authors who have condescended to include blowpipe- 

 operations in their chemical writings, have thought it worth their 

 while to make the least inquiry as to the cause of the phenomenon 

 (1) now under discussion. No doubt, if such men as Plattner or 

 Berzolius had done so, speaking as they would, too. ex oficio 

 (which yoB must not translate by " as a Jack in office "), they would 

 have at once cleared up the matter ; as it is, the following sug- 

 gestion of an ei-artillory officer must be taken in lieu of anything 

 better. As before, we must rest our inquirj- on what that corrupt, 

 old, marvellous judge (t wish we had such judges now-a-days !) 

 and genius, Lord Bacon, called " Induction ; " that is, reasoning 

 from experiment. Most young Englishmen possess uncommonly 

 good eyesight, so that they will find little difficulty in proving the 

 truth of the following extract from my smaller book. " Alphabetical 

 Manual of Blowpipe Analysis," ppge 102. " If tho blast from a 

 mouth-blowpipe be propelled by an operator with good eyesight 

 across the heat-undulations rising from a lighted candle in broad 

 daylight by Irangmitted light, he will see it (the blast) in tho shape 

 of a strai'jht line, about the thickness of a fine sewing-needle. If 

 now he propel a similar blast through tho blue thin flame of a 

 spirit-lamp, which is peiu<tral>le by tho blast, and observe 

 it by reflected light, that is, when ho is between it and the 

 window, ho will again seo it, but this time in tho form of 

 a minntc fono of air, synaxial (that is, formed upon tho 



same line, an it wore) with a flnme-cono projected in tho same 

 dirertiori, from the spirit-lamp. What causig this diffenmco in tho 

 appearance of tho same thing? The only reply to this question 

 si'c-ms to me to bo that a conlined, continued blast apjiears to create 

 round it, in air, a rortez, the gj-rntivo rapidity of which ia least at 

 the commencement, or groatust direct rapidity of the blast, and 

 moKt when that begins to slacken. This aerial vortex is, of course, 

 invisible in air when tho blast is passed throngh the hcat-wavcf 

 above a candle, although the blast itself is perceived there, l>ccauio 

 a space is formed by it within which tho waves themselvos are 

 checked ; but the air-vortex, on tho contrarj-, is distinctly vigiblo 

 when formed within a coloured (blue) fluid of greater consistt^nce 

 than itself, like spirit-flame. It seems obvious, if this explanation 

 bo correct, and tho other fact kept in mind, that tho blast 

 from a blowpipe is not really projected into the candle or 

 oil-lamp pyrocone, but passes over its upper surface, that 

 tho vortex thus created includes within its gyrations the Bame 



blown on one side in the direction of the blast, and force* 

 it to retain a horizontal position, as well as its ovm conical 

 form. It follows from this, that in order to produce a perfect 

 pyrocone, there should be a constant ratio between the strength 

 of tho blast (or air pressure) and the size or bulk of the flame 

 acted on — and this is the fact." If the blast be now propelled 

 into a spirit-lamp flame held about half-an-inch in front of 

 the point marked OP in the figure, that is, about half-an-inch 

 distant from the apex of the ai-rial vortex, a short inverted cone of 

 large diameter appears ; and this, according to Sir J. Herscbd 

 (Essay on Meteorology, page G7) is "a necessary consequence of 

 the vorticose motion." Tho existence of this atmospheric vortex 

 may bo further confirmed by holding about three inches of the 

 finest platinum wire, which has very considerable "spring" or 

 elasticity in it, so that one end just touches the left side of the 

 blowpipe pyrocone. That end will immediately commence a 

 series of gyrations, from left to right, rapid in direct proportion 

 with the strength of the blast, and therefore with the shortness of 

 the diameter of the base of the cone. Another proof is obtained by 

 holding an extremelv hot bead — as nearly red-hot as possible — 

 of fresh P. acid just under the base of the pyrocone ; when a 

 "mantle" of pale green flame surrounds the blue pyrocone, 

 spreading from base to apex. This "mantle" consists of in- 

 finitely small particles of the volatile phosphoric acid burning 

 in the vortex of intensely heated air surrounding the pyrocone. 

 But the most conclusive evidence of all — evidence which seems to 

 mo simply confirmatory of the fact — is this :- — An elastic, expansible 

 cone, such as that formed by an aii'-vortex, must, if compressed at 

 its base, extend in the direction of its gyrations. This is a self- 

 evident law of Dynamics,* and I can never forget the delight with 

 which I found, when I placed a globular ])latin\im dish so that its 

 curved bottom almost touched the base of the blue pyrocone, and 

 thus was bound to squeeze the aii-vortex at its commencement, that 

 my pyrocono instantaneously increased in length at least half on 

 inch. 



We thus possess in this hypothesisf — for, of course, chemists will 

 not allow, for another ten years at least, that there is here the absCK 

 lute proof of the existence of these facts which they have obtained 

 of the existence of proportional atoms — a simple and " pretty " ex- 

 planation, not merely of the conical shape of the " flame " or fire, 

 but of the oxydising properties of tho position OP; of the still 

 more intensely oxydising properties of the position PP. whore the 

 inverted aerial vortex exists; and of the hydrogenising or 

 " reducing " properties of the position IIP ; that is, of the inside of 

 the solid blue pyrocone, which, according to the present accepted 

 " theory " of blowpipe pyrocones, must be full of oxygen contained 

 in the air of the blast. 



But, as the poor ghost in " Hamlet " says (at the beginning, by 

 the way, instead of tho end of his oration), " My hour is almost 

 come ; " and space permits no more on this head at jiresent, so that 

 I must reserve tho discussion of tho other chemical and physical 

 clTects mentioned, for Lesson VI. 



• Oreek, Dunamis, power ; he branch of Physics which treats of 

 bodies in motion, as opposed to Statics. 



t "Hypothesis, a supposition. Something not proved, bnt as 

 Bumcd for tho purpose of argument " (Ogilvio's Dictionary). 



