434 FRAGMENTS OF SCIUNCE. 



stricter continuity. And Mr. Glaisher will inform yon, 

 that if our hypothetical shell were lifted to twice the 

 height of Mont Blanc above the earth's surface, we should 

 still have the azure overhead. By day this light quenches 

 the stars; even by moonlight it is able to exclude from vision 

 all stars between the fifth and the eleventh magnitude. It 

 may be likened to a noise, and the feebler stellar radiance 

 to a whisper drowned by the noise. 



What is the nature of the particles which shed this 

 light? The celebrated De la Rive ascribes the haze of the 

 Alps in fine weather to floating organic germs. Now the 

 possible existence of germs in such profusion has been held 

 up as an absurdity. It has been affirmed that they would 

 darken the air, and on the assumed impossibility of their 

 existence in the requisite numbers, without invasion of the 

 solar light, an apparently powerful argument has been 

 based by believers in spontaneous generation. Similar 

 arguments have been used by the opponents of the germ 

 theory of epidemic disease, who have triumphantly chal- 

 lenged an appeal to the microscope and the chemist's balance 

 to decide the question. Such arguments, however, are 

 founded on a defective acquaintance with the powers and 

 properties of matter. Without committing myself in the 

 least to De la Rive's notion, to the doctrine of spontaneous 

 generation, or to the germ theory of disease, I would 

 simply draw attention to the demonstrable fact, that, in 

 the atmosphere here, we have particles which defy both the 

 microscope and the balance, which do not darken the air, 

 arid which exist, nevertheless, in multitude sufficient to re- 

 duce to insignificance the Israelitish hyperbole regarding 

 the sands upon the seashore. 



The varying judgments of men on these and other 

 questions may perhaps be, to some extent, accounted for 

 by that doctrine of Relativity which plays so important a 

 part in philosophy. This doctrine affirms that the impres- 

 sions made upon us by any circumstance, or combination 

 of circumstances, depend upon our previous state. Two 

 travelers upon the same hefght, the one having ascended 

 to it from the plain, the other having descended to it from 

 a higher elevation, will be differently affected by the scene 

 around them. To the one nature is expanding, to the 

 other it is contracting, and impressions which have two 



