32 THE STORY OF THE BACTERIA. 



which was urged with a good deal of persist- 

 ency some years ago for finding out if there 

 were inhabitants in the moon, and for com- 

 municating with them. 



It was proposed to build in outline on some 

 great plain on the earth's surface, like that of 

 Siberia, a gigantic structure so large that even 

 assuming that the lunar inhabitants had no 

 telescopes, it would be visible to them. This 

 structure was to have some simple suggestive 

 mathematical form like a circle or triangle. 

 Seeing such a thing appear on the earth's sur- 

 face, it was thought that the lunar inhabitants 

 would probably " catch on " this phrase was 

 not known in those primitive times and erect 

 a similar structure, and thus communication 

 would be established. The moon project fell 

 through, but as we have seen by a somewhat 

 similar device, we actually make the inhabit- 

 ants of an unseen world communicate to us 

 to-day some of the secrets of their hidden life. 



But the knowledge derived from the mode 

 of growth of bacteria on potatoes is limited, 

 because as the potato is opaque we can see 

 only the surface of the colony ; and, further- 



