24 PHYSICAL SCIENCE BK. i 



brightness as in the former. But surely no clouds 

 resemble mirrors to this extent. We often pass 

 through the middle of clouds without seeing our 

 selves in them. People who climb to the tops of 



3 mountains look down on cloud, but cannot make 

 out their reflection in it. True enough, 

 but it is separate drops that are separate mirrors, 

 says my opponent. Admitted. Still, I deny 

 that a cloud consists of fully formed drops. It 

 no doubt contains the elements from which the 

 drops are formed, but not as drops. Clouds do 

 not contain even water, but only the material to 

 form water. Granting, for the sake of argument, 

 that there are countless drops in the clouds and 

 that they can reflect an object, yet they do not 

 all produce one and the same reflection, but each 



4 its own. Further, you may join mirrors to one 

 another, but they will not unite to form a single 

 reflection : each portion will enclose a likeness of the 

 object. Some mirrors are composed of a large number 

 of very small parts. Set before them one man and a 

 whole people is reflected, each portion producing an 

 image of its own. The portions of the mirror thus 

 united and placed side by side none the less keep 

 their images separate, and out of one man make 



5 a crowd. But they do not blend in one that 

 troop ; they separate and distinguish the individual 

 faces. Now, a rainbow is bounded by a single 

 outline, the whole presents but one representation. 



Well, but, says our opponent, is not the water 

 that is scattered from a burst pipe, or that is 

 tossed up by the oar, wont to exhibit something 

 similar to these colours that are seen in the bow ? 

 True, but not for the reason which you wish to 

 bring out, to wit, that each single droplet receives 



