254 



• KNOWLEDGE • 



[J AX. 20, 1882. 



iiotism being of nn oppoBito name to tliat magnetism which resides 

 at the north-point iiiK end of the noedlo, and, therefore, attrnctiou 

 ensues, wouhl be little to \Y. H. P.'« purpose, lie desires, most 

 probably, to kuutr how the terrestrial magnetism got there. 



It seems to me the following view (touched upon in some toxt- 

 Iwiokrt) is the most witisfactory : — \Vhono\'cr heat Hows in n closed 

 circuit, there is a flow of positive ehjctricity witli it. If, therefore, 

 II positive current jmsses in the direction indicated by the arrows in 

 Fig. 1, the piece of soft iron would become— so Icmp ns the heat or 

 electricity circulated — an electro-magnet. If to the upper end, 

 marked S, of the soft iron, we were to |>resent tliat end of a mag- 

 netic needle whicli pointed southward (goographioally speaking), we 

 should find that would be repelled, while the north-pointing end of 

 the needle would bo (|uite violently attracted. 



The earth, during her daily rotation, offers succcssivoly 

 ports of her surface to the wanning action of the sun, and 

 !i slight consideration will show that this is practically the 

 same as heat continually passing round the earth in a westerly 

 direction, therefore well representing a closed circuit. We 



have then all that is necessary for tlie state of things above 

 noticed. The wire (Fig.) E.W.w. may well show or rejjre- 

 sent the surface of the earth exposed to the warming action of the 

 snn (for the current will be in the same direction, viz., E.W.w.), the 

 bar, SN, the iron contained in the earth. This iron becomes con- 

 verted into a huge electro-magnet. We should then have towards 

 the Jmrthem part of the earth the same-named magnetism as at 

 position S in the figure. The behaviour of a needle under these 

 circumstances wc have shown ; so a needle on the earth will act in 

 precisely the same manner — that is to say, its N-pointing pole turns 

 to the north, because the different -named magnetisms (if I may use 

 the term) attract. Strictly speaking, there is a fourfold force 

 acting, two on either pole of the needle, one pulling, the other 

 pusliing, not in t)ie sense of moving merely directive ; but, in order 

 to simplify, wo liave neglected the other three. Their action needs 

 no explanation, for they are all additive to the result. — G. F. J. 



THE DESCENT OF MAN. 



[217] — Mr. Donb.avand's method of critici.sm, regularly adopted, 

 would cripple scientific inquiry. He asserts the fir.st difficulty of 

 the evolution theory to be its foundation, comjilaining that it cannot 

 give an exact definition of the period and the form in which the first 

 living organism appeared upon our planet. Now I submit that a 

 similar argument could be advanced, and with eciual force, against 

 the fundaraeutal facts and theories of almost every branch of know- 

 ledge. The chemist bases most intricate calculations upon a hypo- 

 thesis of atoms and molecules, of which not one has ever been seen 

 isolated, weighed, or defined. The electrician speaks habitually of 

 magnetic fluids which have never tangibly revealed themselves. 

 No definite origin can bo assigned either to molecules or to mag- 

 netism. Instances of this kiud might be multiplied ad infnitum. 



Science caimot and does not, as yet, pretend to any knowledge of 

 the beginnings of law, matter, or life. Its present task is to procure 

 and to sift evidence, to arrange and to explain known facts, and 

 thereupon to formulate certain theories which shall enable us, 

 reasoning by analogy, to acquire a more correct and comprehensive 

 view of the subject of inquiry. 



Darwin and his followers are stai^'il by the highest authorities to 

 have effected much in this direction. But, in any event, I contend 

 that there is no scientific reproach to their theory in the circum- 

 stance that it fails to demonstrate the absolute origin of life. It is 

 no evidence against the continued straightness of a line that our 

 vision cannot extend to its extremities. E. BfRKE. 



"A GLIMPSE THROUGH THE CORRIDORS OF TIME- 

 LIGHT AND HEAT WAVES." 



[218] — Jl writer in Nature calls attention to a paper published by 

 Kant, when he was thirty years of age, iu wliich he states, " If the 

 earth were a perfectly solid mass, without any litpiid, the attractions 

 of the sun and moon would not alter the rate of rotation round the 

 axis .... If, however, the mass of a planet includes a con- 

 siderable amount of liquid, the attraction of the sun and moon, by 



moving this liquid, impress upon the earth a part of the Tibralioni 

 thus produced. The earth is in this condition." Ho then 

 goes on (soys the writer) to state that the moon produce* 

 the greatest cflect and the tide running round tho earth in a direc- 

 tion opposed to that of rotation. " Wo have hero a causo on which 

 wo can count with certainty, incessantly reducing this rotation bjr 

 as much us it may be capable of." ... " When the e.arth steadily 

 draws nearer and nearer to tho end of its rotation, this period of 

 change will bo completed when its surface is, relatively to tho moon, 

 at rest, i.e., when it rotates ronnd its axis in the same time in which 

 the moon revolves round it, and will, consequently, always show 

 the same face to the moon. ... If tho earth were entirely fluid, 

 tho attraction of the moon would very soon reduce its rotation to 

 this minimum. Herein we at once see a cau-ie why the moon 

 always shows the same face to the earth. . . . From this we may 

 conclude with certainty that when the moon wa.s originally formed 

 and still fluid, tho attraction of the earth must in the manner abovs 

 described have reduced the speed of rotation, which then, in all 

 probability was greater, to the present measured limit." 



The writer considers that Kant had given a glimpse through tho 

 corridor of time a centurj' earlier than any of the authorities 

 mentionefl by Professor Ball. 



Do light and heat travel at tho same pace ? Do tho waves of 

 light and heat coincide ? — which, I supiwse, may be only aiujther 

 way of asking the same question. — A. T. C. 



[Light waves are, for the most part, heat waves, and vice verti, 

 though the luminous effect of different ether waves is not propor- 

 tional to the heating effect. Of such waves we may say that tliey 

 do not coincide, being identical. The same things cannot coincide, 

 any more than a horse can run a dead heat with himself. — Ed.] 



PLATING ALKALOIDS. 



[210] — Mr. Lewis Arundel has failed to answer tho point in 

 query 152 that I wanted elucidating, viz., how to plate on iron. 

 Having tried silvering on iron in tho wet way, first coating mth 

 copper, and failed in this, I am anxious to try nickel. In Supple- 

 ment II., Watts' " Die. Chem.," the neatest method of nickel- 

 plating on copper and brass is given. With regard to the letter on 

 alkaloids, Watson Smith (Bcriiht's " Deut. Chem. Gcsellschaft," 

 xii., 1,420) gives antimony or bismuth trichloride as a test for 

 several alkaloids, including aconitiue, which gives a bronze-brown 

 colour. Again, last year (Thresh gives in " Pharm. J. Trans." [3], 

 X., 800, a metliod of estimating the quantity of this, and of other 

 alkaloids present, by precipitation with iodide of potassium and 

 bismuth.— C. T. B. 



THE HEALTH OP NAVVIES. 



[220] — After reading your abstract from the Times on the above, 

 it occurred to me that M. Colin might now very advantageously 

 try what the effect the betel nut would have in warding off the 

 malarias, &c., contracted in marshy grounds. I think Johnson, in 

 his " Chemistry of Common Life," informs us that the betel 

 chewer, whether native or stranger, has an invaluable treasure in 

 the use of tlijs narcotic, which is a perfect safeguard against fevers, 

 agues, and all other maladies incidental to marsh life. It this is 

 the case, is it not worth a trial during the extensive canalisation 

 soon to be done in France ? M. Colin, should he try it, would be 

 able to see if tho effect of betel by itself is the same na when 

 chewed with the betel pepper leaf, and quicklime. F. C. S. 



SCIENTIFIC PARADOX. 



[221] — The difficulty of '• Eclecticus " (p. 202) may possibly 

 arise from his conception of the manner in which the pressure of a 

 gas or vapour arises. Liquids have a tendency to give off vapour 

 to a greater or less extent. This tendency varies mth different 

 liquids, and in the case of the same liquid, varies with differences of 

 temperature. But vapours have a tendency to condense into the 

 liquid form dependent npon their nature and the comiitions to 

 which they are expo.sed. When these two antagonistic inflnences 

 are in equilibrium, a state of stability arises. Now, although there 

 may bo an atmosjihere of ether-vaiiour present, water will continne 

 to evaporate cither nntil the tendency of the water to vaporise is 

 coiinterlmlanced by the tendency of the water-\-apour to liquefy, or 

 until no liquid water remains. It is evident the ether-vapom* takes 

 no part in producing this equilibrium, merely retarding the forma- 

 tion of vapour, and going to increase the total pressure. 



It may be added that the total pressure exerted in the case of 

 tho vapours of ether, alcohol, and water is very much loss than tho 

 sum of their individual tensions. This only holds good for liqnids 

 which do not dissolve in one another. W. S. C 



