THE DTATOMES. 351 



in my streams would afford occupation for a long lifetime. At present 

 the microscopists are only upon the fringe of the subject. They 

 have not discovered the accurate and complete natural history of a 

 single diatome. These siliceous plants have been so common in some 

 part of the world's history that thick fossil beds of great extent have 

 been discovered which are one mass of them. At Richmond in America 

 there is a bed of these fossils twenty miles long and several feet in 

 depth. Polishing powders usually contain these siliceous particles, and 

 guano is said to contain a large proportion. As there is reason to 

 suppose that some fish use them for food, I have caused the intes- 

 tines of young trout to be examined for them, but \vithout success. 

 In the natural state they are more beautiful than in the dead skeleton 

 form which is so attractive to many members of the microscopical 

 Societies. The Melosira varians looks like a number of hat-boxes 

 placed end to end. The Meridian circulare resembles a wheel with 

 its spokes. The Diatome vnlgare resembles a flight of stairs. The 

 examination of the growing species in our little streams is replete 

 with interest. 



MOSSES. 



There are not many species of Moss in my garden, although 

 between four and five hundred species are 

 found in Great Britain. We have however, in 

 the river, growing abundantly in some situa- 

 tions, the Fontinalis antipyrctica (fig. 815), 

 which contains so much silex that it is used 

 by the Laplanders to prevent their wooden 

 houses from burning. 



The Funaria hygromctrica (fig. 816) grows 

 freely in my garden, and is an interesting 

 object. 



To observe this class of the lower plants Fir " 8 '5- Fontinalis 

 more attentively a mossery has been planted in the fern glen ; but an 

 unforeseen difficulty occurred which never could have been anticipated: 



