2 7 ( S 6) 



it is possible to state with great distinctness which ves- 

 sel contains the largest particles. 



The eye is very sensitive to differences of light, when, 

 as here, the eye is in comparative darkness, and when 

 the quantities of wave motion thrown against the retina 

 are small. The larger particles declare themselves by 

 the greater whiteness of their scattered light. Call now 

 to mind the observation, or effort at observation, made by 

 our president when he failed to distinguish the particles 

 of resin in Briicke's medium, and when you have done 

 so follow me. I permitted a beam of light to act upon 

 a certain vapor. In two minutes the azure appeared, 

 but at the end of fifteen minutes it had not ceased to 

 be azure. After fifteen minutes, for example, its color 

 and some other phenomena pronounced it to be a blue 

 of distinctly smaller particles than those sought for in 

 tain by Mr. Huxley. These particles, as already stated, 



must have been less than T o<ro<y<y f an mcn m diame- 

 ter. 



And now I want you to submit to your imagination 

 the following question : Here are particles which have 

 been growing continually for fifteen minutes, and at the 

 end of that time are demonstrably smaller than those 

 which defied the microscope of Mr. Huxley. What 

 must have been the size of these particles at the begin- 

 ning of their growth ? What notion can you form of 

 the magnitude of such particles ? As the distances of 

 stellar space give us simply a bewildering sense of vast- 

 ness without leaving any distinct impression on the mind, 

 so the magnitudes with which we have here to do im- 

 press us with a bewildering sense of smallness. We 

 are dealing with infinitesimals compared with which the 

 test objects of the microscope are literally immense, 



