SCIENTIFIC SIDE-LIGHTS 



Evolution 

 Exactness 



paratus is rarely necessary, and fallacies 

 will generally be avoided by observing two 

 directions. In the first place, the sample 

 should be chosen as representative as pos- 

 sible of the real substance or conditions we 

 wish to examine. Some authorities advise 

 that it is necessary to allow the tap to run 

 for some minutes previous to collecting the 

 sample ; but if we desire to examine for lead 

 chemically or for micro-organisms in the 

 pipes biologically, then such a proceeding 

 would be injudicious. Hence we must use 

 common sense in the selection and obtaining 

 of a sample, following this one guide, name- 

 ly, to collect as nearly as possible a sample 

 of the exact water the quality of which it is 

 desired to learn. In the second place, we 

 must observe strict bacteriological cleanli- 

 ness in all our manipulations. This means 

 that we must use only sterilized vessels or 

 flasks for collecting the sample, and in the 

 manipulation required we must be extremely 

 careful to avoid any pollution of air or any 

 addition to the organisms of the water from 

 unsterilized apparatus. A flask polluted in 

 only the most infinitesimal degree will en- 

 tirely vitiate all results. NEWMAN Bac- 

 terid, ch. 2, p. 37. (G. P. P., 1899.) 



1115. 



Disregarded by 



Popular Writers. Hitherto the endeavor of 

 assigning these levels [of animal intelli- 

 gence] has been almost exclusively in the 

 hands of popular writers; and as these 

 have, for the most part, merely strung to- 

 gether, with discrimination more or less in- 

 adequate, innumerable anecdotes of the dis- 

 play of animal intelligence, their books are 

 valueless as works of reference. So much, 

 indeed, is this the case that comparative 

 psychology has been virtually excluded from 

 the hierarchy of the sciences. If we except 

 the methodical researches of a few dis- 

 tinguished naturalists, it would appear that 

 the phenomena of mind in animals, having 

 constituted so much and so long the theme 

 of unscientific authors, are now considered 

 well-nigh unworthy of serious treatment by 

 scientific methods. ROMANES Animal Intel- 

 ligence, pref., p. 6. (A., 1899.) 



1116. Early Disinfecting 



Processes Conspicuously Inexact Working 

 without a Standard. The effects of chemical 

 substances as solutions, or in spray form, 

 upon bacteria have been observed from the 

 earliest days of bacteriology. To some de- 

 composing matter or solution a disinfectant 

 was added and subcultures made. If bac- 

 teria continued to develop, the disinfection 

 had not been efficient ; if, on the other hand, 

 the subculture remained sterile, disinfec- 

 tion had been complete. From such rough- 

 and-ready methods large deductions were 

 drawn, and it is hardly too much to say that 

 no branch of bacteriology contains such a 

 vast mass of unassimilated and unassimi- 

 lable statements as that relating to research 

 into disinfectants. Most of the tabulated 

 and recorded results are conspicuous in hav- 



ing no standard as regards bacterial growth. 

 Yet without such a standard results are not 

 comparable. NEWMAN Bacteria, ch. 9, p. 

 329. (G. P. P., 1899.) 



1117. 



Influence of Height 



upon Combustion Ghostly Flame on Sum- 

 mit of Mont Blanc. To determine the influ- 

 ence of height upon the rate of combustion 

 was one of the problems which I set before 

 myself in my journey to the Alps in 1859. 

 On that occasion I invited Dr. Frankland to 

 accompany me, and to undertake the experi- 

 ments on combustion, while I devoted my- 

 self to observations on solar radiation. The 

 plan pursued was this: six candles were 

 purchased at Chamouni and carefully 

 weighed; they were then allowed to burn 

 for an hour in the H6tel de 1'Union, and the 

 loss of weight was determined. The same 

 candles were taken to the summit of Mont 

 Blanc, and, on the morning of August 21, 

 1859, were allowed to burn for an hour in a 

 tent, which shaded them from the sun and 

 sheltered them from the wind. The aspect 

 of the six flames at the summit surprised us 

 both. They seemed the mere ghosts of the 

 flames produced at Chamouni enlarged, 

 pale, feeble, and suggesting a greatly dimin- 

 ished energy of combustion. The candles 

 being carefully weighed on our return, the 

 unexpected fact was revealed that the quan- 

 tity of stearin consumed above was almost 

 precisely the same as that consumed below. 

 Thus, tho the light-giving power of the flame 

 was diminished in an extraordinary degree, 

 the rapidity of the combustion was un- 

 changed. This curious result is to be as- 

 cribed mainly to the mobility of the air at 

 this great height. The particles of oxygen 

 could penetrate the flame with comparative 

 freedom, thus destroying its light, and ma- 

 king atonement for the smallness of their 

 number by the rapidity of their action. I 

 find, indeed, that by reducing the density of 

 ordinary atmospheric air to one-half, we 

 nearly double the mobility of its atoms. 

 TYNDALL Heat a Mode of Motion, lect. 3, p. 

 64. (A., 1900.) 



1118. 



Light as an Indi- 



cator of Motion The Faintest Thrills of 

 Heat or Magnetism Measured. Now, this 

 law of angular reflection [the law, viz.: 

 that when a mirror rotates, the angular ve- 

 locity of a beam reflected from it is twice 

 that of the reflecting mirror], coupled with 

 the fact that a beam of light possesses no 

 weight, gives us the means of magnifying 

 small motions to an extraordinary degree. 

 Thus, by attaching mirrors to his suspended 

 magnets, and by watching the images of di- 

 vided scales reflected from the mirrors, the 

 celebrated Gauss was able to detect the 

 slightest thrill of variation on the part of 

 the earth's magnetic force. By a similar ar- 

 rangement the feeble attractions and repul- 

 sions of the diamagnetic force have been 

 made manifest. The minute elongation of a 

 bar of metal by the mere warmth of the 



