BEYOND THE LIMITS OF VISION. 15 



kept there for a half an hour or more, every particle of reflecting 

 matter in it will be burned out, and thereafter the track of a sun 

 beam through this air will be as black as through a perfect vac- 

 uum. Now the inorganic material of our world has been long 

 ago all burned up, and there is nothing now that burns except new 

 formed, that is, organic substances. Therefore the sky dust is 

 clearly of organic origin. 



It is well known that the air which covers, and the winds which 

 blow, over the regions of prolific life, and especially the busy 

 haunts of men, are loaded with the gerrns and spores of every 

 kind of infinitesimal organisms. The seeds of decay, of ferment, 

 of disease, and of the myriad forms of infusorial life, must 

 abound in the air which surrounds us. For not an animal ceases 

 to breathe, or a plant to live, or a particle of organic matter to 

 be exposed, but it is in a very short time invaded by the peculiar 

 organism that seems to exist for the destruction of each. 



Now this is not so on. the heights of mountains, or even on our 

 dry western plains. Meats may be preserved, and organic infu- 

 sions kept sweet, when exposed in such localities, for a longtime. 

 Cattle that die on the western ranges dry up before decay sets in, 

 and sealed cans of provisions opened on the higher summits of 

 mountains will remain preserved for any length of time, showing 

 that the germs of putrefaction and ordinary decay do not exist in 

 the dry air of elevated plains nor in the upper regions of the 

 atmosphere. 



But organic matter is there in abundance, for the same deep 

 blue skies are above the highest peaks of the Rocky Mountains, 

 that are over us here to-night. Therefore it is probable that the 

 germ life of the upper skies, whatever it may be, never develops 

 into anything that becomes sensible to our means of observation. 



But I propose, if you will kindly have the patience to follow 

 me, to lead you down some long steps further into infinitesimal 

 magnitudes, to give you an idea of one of the boldest specu- 

 lations in regard to the ultimate constitution of matter, which 

 the mind of man has ever conceived. 



It is common knowledge that the chemists describe and give 

 names to about seventy/ elementary substances, or forms of matter 



