MINERALOGY. - 53 
microscope, as it appeared occupied with a sample of New Hampshire 
infusorial earth.* The species represented are as follows : 
Polygastern. Fig. 17. Himantidium arcus. 
Fig. 1. Chaetophila Saxipara. 18. ee gracile. 
1" , Discoplea Coscinodiscus. ge Navicule a oxy: 
2s zo. ‘  dilitata. 
3. Eunotia icosodon. 21.  “  Jineolata. 
4. “© monodon. 2z. ‘  Legumen. 
5 “*  octonaria. 23. Pinnularia Semen. 
6. «¢  quatuordenaria. 24. “ viridis. 
7 ‘« septenaria. 25. Stauroneis Phcenicenteron. 
Oo 20: { Tabellaria trinodis 
9 ‘*  tredenaria. 27. : 
Io. ‘*  triodon. 28. Trachelomonas? levis. 
Il. a & 29. a pyrum. 
12. ‘¢  undenaria. Phytolitharien. 
13. Fragilaria constricta. 30. Lithodontium furcatum. 
14. Gallionella distans. 31. Spongolithis aspera. 
15. Gomphonema gracile. Soft parts of Plants. 
16. “ truncatum. 32. Pollen Pini. 
These organisms are excessively minute, and a cubic inch of this earth 
contains many millions of individuals. 
Dr. A. M. Edwards has studied these earths, and in Vol. I of this geo- 
logical report will be found a lengthy treatise on the diatomaceze in 
general, with illustrative plates.} The small figures here reproduced 
are sufficient, however, to show those interested in the subject from a 
mineralogical stand-point, the nature and composition of these interesting 
deposits. 
This substance is also of considerable economic value. It is burned 
till it is white, whereby the water and organic matters are removed, and 
it then constitutes the best kind of polishing powder ; for, although they 
are quite hard, the grains are so extremely minute that they scarcely 
feel gritty between the teeth, and consequently the substance is emi- 
Aw ela’ + . : 
maison lee lena Sa Set aes ieee, Shae earth te soluble in caustic 
X. Also, Monatsbericht der Berliner Akad. der Wissenschaften, 
cz 
t Mr. H. L. Smith, of Geneva, N. Y., has also examined these earths, 
s : and is prepared to furni F 
series, embracing all the different species, properly mounted for microscopi Prep rnish a typical 
ic study, 
