earth," vary greatly in appearance as well as in microscopic cha- 

 racter, therefore the following directions will suffice to guide eol- 

 - in >< arching for and detecting them. Gather all earths of 

 a light color, varying from a pure white through different shades 

 of gray, cream, and fawn, to an iron-rust tint. The texture is 

 often friable, at other times of a hard and strong character, though 

 always more or less porous, and when soft of little weight. Infu- 

 sorial earth is occasionally found as a powder looking like flour 

 or meal. In general these deposits have the appearance of clay, 

 and are often taken for that substance. Collect enough to make 

 up a mass of from three to four pounds weight, or a block of six 

 or eight inches square, and, if possible, from the surface, and at 

 different depths. Keep all specimens separate, not even permit- 

 ting them to come in contact, by wrapping each in "a paper, plac- 

 ing within a label having written upon it in ink the exact locality, 

 date of collection, and name of collector. It is also desirable, if 

 possible, to state the depth from the surface, together with any 

 farther information that may be deemed of interest, as supposed 

 extent of the stratum ; slope, upwards, towards north, south, east, 

 or west, and thickness. 



Besides the above mentioned an extremely interesting stratum 

 of a similar character, but in general of a harder texture, has 

 been found on the Pacific coast of Xorth America at Monterey 

 and San Diego in California. Between these two points no re- 

 cord of its occurrence has been made ; it becomes, therefore, of 

 importance to trace it from one to the other of these localities 

 and eastward to the mountains. 



At Baldjik near Varna, in Bulgaria, on the Black Sea, is a 

 stratum of a stony character, having shells and bones dispersed 

 through it. But very little of this material has found its way 

 into the hands of naturalists. 



At Oran in Algeria, Africa, and at iEgina and Caltanisetta in 

 Greece are deposits of marl belonging to the cretaceous period. 

 The marls of the island of Barbadoes are also calcareous in cha- 

 racter, and besides Diatoms contain beautiful specimens of Poly- 

 cystina. A deposit has been lately discovered in the island of 

 Trinidad at South Xaparima, and "is considered as connected 

 with the New Red Sandstone; adjoining to which is the sand- 

 stone, probably of the same description, in which the Pitch Lake 

 is situated." 



