248 



KNOWLEDGE 



[N0\'EMBEB 1, 1899. 



ferent authorities at from two to four pounds, and partly 

 by the natural loss of weight from obvious causes. It 



would be a simple courae to weigh the excreta : but has 

 this been done ? 



The foregoing are the average weights of a healthy man, 

 engaged in ordinary work ; however, fuller observations 

 are certainly wanted. 



Some very curious records of variations in body- weight 

 at different times in the year have been given by a Danish 

 observer, Mr. Hansen, but these are what may be called 

 periodic phenomena. If children be studied — and these 

 are more closely related to the lower forms of animal and 

 vegetable life than are adults — periods of growth, of fatten- 

 ing, and of equipoise are distinguishable. Mr. Hansen, of 

 Copenhagen, from a very large series of observations of 

 children, shows that there is an increase of weight from 

 August to December, and a season of growth from April 

 to August, and a period of rest both in weight and growth 

 from December to April. These observations, however, 

 do not touch the question which this paper tries to make 

 rather clearer — that of daily variations in body-weight in 

 a healthy person. 



If any one were careful to take similar observations in 

 asylums, infirmaries, and hospitals, it is quite possible 

 some difference might be found according to age, sex, and 

 conditions of disease, and it is possible there might be 

 a difference according to nationality. 



What has been learnt from the weighing of a fasting man 

 at different times ? And would not periodical weighing 

 help to detect some of the shammers ? 



I think it will be seen from the above that it is important 

 to choose the time for weighing a recruit, or even a person 

 submitting himself to life insurance, and is it not a matter 

 of interest to all of us to learn a little more about om-selves 

 in any way ? 



IS THE STELLAR UNIVERSE FINITE? 



By Gavin J. Burns, b.Sc. 



IN my paper on the " Distribution of Stars in Space,"* 

 I advanced some facts and observations which tend 

 to show that the number of faint stars is much 

 smaller than it would be on the hypothesis that 

 stars of all degress of intrinsic brightness are 

 uniformly distributed throughout space, and so the stars 

 present the appearance of thinning out as we recede from 

 the solar system. 



There appear to be four possible hypotheses as to the 

 probable cause of the reduction in the number of faint and 

 telescopic stars : — 



1. Absorption of light by the luminiferous ether. 



2. Absorption of light by a gas filling interstellar space. 



3. Absorption of light by cosmical dust. 



4. A progressive decrease in the density of stellar 

 aggregation as the distance from the sun increases. 



The loss of light in passing through a semi-transparent 

 medium will augment as the distance increases and the 

 light of the most distant stars practically obliterated. 



1. We may dismiss the hypothesis that a plane wave of 

 light diminishes in amplitude in traversing the luminiferous 

 ether as being void of experimental foundation ; moreover, 

 it is difficult to reconcile with the law of the conservation 

 of energy. When light is absorbed in its passage through 

 a material medium, it is transformed into heat, and the 

 medium is warmed ; but in traversing the ether, what 

 would become of the heat ? 



2. Regarding the hypothesis that the interstellar spaces 

 are filled with matter in the gaseous form, matter can only 

 exist in the attenuated state when above a certain tempera- 

 ture, and in extra-terrestrial space a cold obtains akin to 

 absolute zero in which known gases would be congealed; 

 besides, if a gas were diffused throughout space, we should 

 expect to see its absorption lines present in the spectra of 

 all stars, but no such lines have been observed. 



3. Absorption of light by cosmical dust must be regarded 

 as not only possible but probable ; the only pertinent 

 question which presents itself is — what is the quantity 

 distributed and the amount of light it can intercept '? 

 Suppose that at some remote period of time cosmical dust 

 was densely scattered throughout aU space, producing an 

 effect ou the light of the stars like that of a terrestrial fog, 

 causing the nearer lights to be dimmed, and the farther 

 ones entirely obscured ; then, if these particles of dust were 

 originally at rest, they would not remain so ; for, since 

 gravitation is universal, each particle would begin to move 

 towards some centre of attraction and its motion continue 

 with ever-increasing velocity till it reached the attracting 

 centre ; thus, in a comparatively short space of time, the 

 whole of the cosmical dust would aggregate around the 

 larger masses which might, or might not, be lucid stars. 

 If the particles of cosmical dust were originally in motion, a 

 like result would follow, the time required being greater, 

 for each particle, moving till it came within the influence 



• See Knowledge, Julv, 1899, p. 152. 



