•IS 



♦ KNOWLEDGE ♦ 



[Maboh 17, 1882. 



>f what may bo called tho " atraosphcro of spacn," from 

 Analysis of tlic gnsrs loi-kodup in froshlyfalloii mot<'orites, 

 which sonictiinrs " oicliidt" kIx times their own hulk. A 

 recent aniilysis l>y Dr. Klij^ht guve nearly 4C per cent of 

 tho Uiia\ as consistinj; of hydrogen, .''."J pr>r cent, of carbonic 

 oxide, and IH per cent of nitrogen ; and it soenis clear 

 that the liyclrogea and carbonic oxide could not have been 

 absorbed during tho pas.sagc of the niet<'orite througii our own 

 atmosphere, but must have betm lirought in from the out- 

 side. Further proof that .stellar s]iace is lilled with gaseous 

 matter is furnished by spectrum analysis ; and the recent 

 invojitigutions of Dr. II\iggins and others into the compo- 

 sition of the last groat Comet showed it to contain very 

 much the same gases with tho.se contained in meteorites. 



II. It was long since shown by Sir William Grove 

 that water can be decomposed — or, in modern chemical 

 language, that oxygon and hydrogen can be "dissociated" 

 — by heat alone ; and wo know that the dissociation 

 of tho oxygen and carbon in carbonic acid, is effected 

 \>y light, acting through certain vegetable substances. 

 Now, according to the law of dissociation developed 

 by Bunson and Saint Claire Deville, the point of dis- 

 sociation of dill'erent compounds depends upon tempera- 

 ture on tlie one hand and pressure on the other ; so that it 

 is quite conceivable that when aqueous vapour is reduced 

 to extreme tenuity, its dissociation may be effected by solar 

 radiation at a coniimratively low temperature. Some years 

 ago Dr. Siemens tried some experiments on this point, 

 the results of which were (so far as they went) con- 

 tirmatory of this view. And his recent well-known ex- 

 periments on the growth of plants under the electric light 

 have satisfied liim that, provided the source of the light 

 give it off in sufficient inti'iisih/, the quantil)/ required is 

 very small. And he is thus led to suggest that all the 

 i-adiant energy which is seemingly running to waste, is 

 really doing work in dissociating the aqueous vapour and 

 I'arbonic acid of the " sjiace atmosphere," the carbon being 

 thus made ready to unite with the nascent hydrogen into 

 combustible hydrocarbons. 



III. The third basis of Dr. Siemens's doctrine is the 

 effect that will be produced by the rotation of the Sun 

 around its axis, on the distribution of gases and vapours in 

 its atmosphere. The tangential velocity of the sun at its 

 equator being nearly four times that of our earth, an ex- 

 tension of the solar atmosphere must take place in the 

 equatorial plane, to which (revi\ ing an old hypothesis, and 

 explaining away the objection raised to it by Laplace) Dr. 

 Siemens attributes the "zodiacal light." Pressures being 

 balanced all round, Dr. Siemens shows that the sun would 

 be continually di-awing hydrogen, hydrocarbons, and oxygen 

 from the " space atmosphere " towards its polar surfaces, 

 and be continually projecting outwards the products of 

 their reunion, from the equatorial extension of its own 

 atmosphere. During their gradual approach, they will pass 

 from their condition of extreme attenuation and extreme 

 cold to that of compression, accompanied with rise of tem- 

 perature ; until, on approaching the photosphere, they 

 liurst into flame, giving rise to a great development of heat, 

 and themseUes acquiring a temperature proportionate to the 

 pressure they are sustaining. The result of their com- 

 Im.stion will be aqueous vapour and carbonic oxide or 

 lyirbonic acid, according to the sufficiency or insufficiency 

 of tlie oxygen present to complete the combustion : and 

 these products of combustion, yielding to the influence of 

 . entrifugal force, will flow towards the solar equator, and 

 he thence projected into space. 



In this manner a continual interchange of matter will be 

 taking place between the sun and its " environment ;" and as 

 the Sun is constantly and rapidly moving through space, it 



will be continually traversing now portions of the "space- 

 atmosphere," wliich, it is conceivable, may be so differently 

 charged with the supplies of material, as to be more or less 

 potent in maintaining tlie solar energy. 



Such is a general outline of Dr. Siemens's most ingenious 

 spectdation, which, whatever may be its ultiniatf- issue, 

 must bo accounted one of the highe.'.t and most brilliant 

 flights that the " .scientilic imagination ' has ever made. 

 Such as desire a more detailed exposition of it — especially 

 as to tho changes which Dr. Siemens supposes to be always 

 taking place on the surface of the sun itself — will find it in 

 his papiT, which will speedily appear in the " Proceedings 

 of the Royal Society." Its publication will douV)tless give 

 rise to mucli discussion : and, whatever may be tho ultimate 

 fate of the doctrine as a physical theory, there can be no 

 doubt that in the new direction which it will give to 

 investigation, its promulgation will contribute in no small 

 measure to tho advance of science. 



NOTES ON ROWING. 



By .\n Old Club Captain. 



LET us, in the first place, consider the conditions under 

 which an ordinary lap-streaked inrigged (or half out- 

 rigged) boat should be rowed in order to get the best 

 racing speed for a boat of that sort. I, of course, ossurue 

 the rower to have mastered all the initial difficulties of his 

 art, so as to be able to give his attention to tho question of 

 style. Well, in the first place we find that for racing 

 purposes the great object is to adopt a style by which we 

 may niaiiilaiii, as far as possible, the velocity which can be 

 readily enough communicated by a great short-lasting effort, 

 and to do this with as little o^erwork as possible. Racing 

 necessarily involves overwork, for no one who meant to 

 row for two or three hours, or even for a single hour, 

 would adojjt a racing stroke, even for tivt? minutes of the 

 time. But tho overwork in a race has to last over a good 

 many minutes, and must be so distributed as to be most 

 effective. The rower has, therefore, in racing to avoid, 

 above all things, whatever would invohe waste of power ; 

 and he very quickly finds that the most mischievous waste 

 of power results if he suffer the extra speed communicated 

 by his efforts to be lost more than of necessity it mtut be 

 lost between the strokes. In other words, a given average 

 of velocity is obtained with greater or less expenditure of 

 force, according as the necessarily varying velocity of the 

 lioat ranges more or less above and below that average. 

 Or we may put the matter this way (it is not without a 

 purpose that we put it in both ways) : The more uniform 

 the velocity, the less the total expenditure of power to 

 attain a given average rate of speed. 



When we say that a rower soon finds this out, we mean 

 that if he is attentive and apt he does so. As a matter of 

 tact, the most successful oarsmen (in races) are those who, 

 whether they know it or not, have practically found this 

 out, and the rules for a good rowing style are based — as 

 will presently appear — on this important principle. But 

 we know that, apart froui training and example, numbers 

 of stout oarsmen would never attain a good rowing style, 

 or at any rate a good racing style. So that we might 

 probably have said more truly that nine-tenths of our 

 rowing men would not of themsehos discover this law, 

 which comes out very gradually in rowing practice, even 

 to till' acuter rower, and is theoretically only to bo 

 established by somewhat difficult reasoning, based on 

 recondite jirinciples, partly dynamical, partly physical, 

 and partly physiological. 



