8 BEYOND THE LIMITS OF VISION. 



shriveled skin. These spores, at first too small to be resolved by 

 the highest powers that our microscopist could bring to bear upon 

 them, soon however grew to be visible as distinct points, then to 

 push out their little threads of locomotion, and at length to 

 become the full grown monads, ready to commence the other 

 kind of generation, that of self-division. You can any of you 

 easily repeat at least some part of this experiment, by putting a 

 bit of fresh meat into a tumbler of water and letting it stand for 

 a few days. You will then have a crop of infusoria that literally 

 " no man can number." They would not probably be the identical 

 species experimented upon by Dallinger, but one no larger and 

 having an entirely similar life history and modes of generation. 



I have estimated in regard to Dallinger's monads that a hun- 

 dred million of them, great and small, might be contained in a 

 drop of water, and yet be no more crowded than I have seen 

 bacteria in infusions. Theoretically the natural increase of one 

 of these germs dropped into an infusion, and within twenty-four 

 hours, would be numbered as the figure one followed by eighteen 

 ciphers. Now as this would be as many as a good sized pond 

 would hold, we must suppose that the cruel principle of the 

 survival of the fittest comes into that community long before it 

 is twenty-four hours old. 



But we must hasten our steps. We have not passed below the 

 microscope as yet, and we have a long journey downward still 

 to make. I will first endeavor to give you some idea of Molecu- 

 lar Physics of the conditions and sizes of the ultimate particles 

 which compose the matter about us. I do not however dare to 

 present to you the array of figures which are necessary to show 

 the relations and dimensions of the molecules, without giving at 

 least an indication of the methods by which they have been 

 found out. You would not begin to believe me if I did not have 

 some show of proof to offer. So at a risk of appearing a 

 little abstruse, and perhaps of not being fully understood for a 

 few moments, I will attempt to tell you how the scientists have 

 been, able to come at the ultimate molecules of matter, so totally 

 below the reach of manipulation, or the highest powers of the 

 microscope. 



