4 NATURE AND LIFE. 



serve how the amazing revelations of the microscopic world 

 have justified his eloquence and foresight ; and yet this mi- 

 croscopic world, whose minutest representatives, such as 

 vibrios and bacteria, are hardly less than the ten-thousandth 

 part of ^5- of an inch, how coarse it is compared with the 

 particles thrown off by odorous bodies, and with the incon- 

 ceivably minute quantities which chemistry, physics, and 

 mechanics, now measure without seeing them, or make 

 their existence plain without grasping them. We may 

 mention some instances which can give us an idea of these. 

 According to Tyndall, when very minute solid particles, 

 smaller than the luminous waves, are diffused in a medi- 

 um traversed by light, the light is decomposed in such a 

 way that the least waves, the blue ones, predominate in 

 the reflected rays, and the largest ones, the red waves, in 

 the transmitted rays. This ingenious physicist thus ex- 

 plains how the blue color of the sky depends and must de- 

 pend on the existence of solid particles, excessively minute, 

 diffused in infinite quantity through the atmosphere. Tyn- 

 dall is not disinclined to the idea that these imperceptible 

 atoms might very well be no other than those germs of 

 microscopic organisms the presence of which in the atmos- 

 phere has been proved by the labors of Pasteur, as well as 

 the part they take in the phenomena of putrefaction and fer- 

 mentation. The ova of these beings, which are barely vis- 

 ible under the microscope after attaining full development, 

 and of which the number, ascertained by the most decisive 

 evidence, confounds the boldest imagination, these would be 

 the elements of that vital ether, as we have termed it, that 

 dust which gives its lovely blue tint to the vault of the sky. 

 " There exist in the atmosphere," Tyndall says in closing, 

 " particles of matter that elude the microscope and the scales, 

 which do not disturb its clearness, and yet are present in 

 it in so immense a multitude that the Hebrew hyperbole 

 of the number of grains of sand on the sea-shore becomes 



