256 UTILIZATION OF MINUTE LIFE. 



cretaceous greensands of England contain, unmis- 

 takeably, these stony casts. In the Tertiary com- 

 pact, limestone and nummulitic limestones, occur 

 beautifully preserved specimens of Quinqueloculina, 

 Rotalia, Textularia, Grammostoma, and Alscolina. 

 In the lower Silurian greensand casts of detached 

 cells of Textularia and Nodosaria have been 

 found." 



In the lakes of Sweden there are vast layers of 

 iron oxide almost exclusively built up by animal- 

 cules. This kind of iron-stone is called lake-ore. 

 In winter the Swedish peasant, who has but little 

 to do in that season, makes holes in the ice of a 

 lake, and with a long pole brings up mud, etc., 

 until he comes upon an iron bank. A kind of sieve 

 is then let down to extract the ore. One man can 

 raise in this manner about one ton per diem. 



Besides the excellent polishing material fur- 

 nished by these infusorial deposits, Liebig has 

 recently drawn attention to another application of 

 which they are susceptible. His observations were 

 made upon an infusorial deposit which constitutes 

 the under soil of the commons or plains of Liine- 

 bourg, in Germany (Fig. 34) ; and he has shown 

 that these microscopic remains, as well as those 

 taken from several other localities, can be very 

 easily converted into silicate of potash or silicate of 

 soda, sometimes known as " soluble glass." It was 



