172 



INFUSORIA. 



SILICIOUS INFUSORIA. 



Many ponds are inhabited by myriads of microscopic animalcules, whose skeletons, 

 when the animals die, fall to the bottom, and in process of time form deposits of fine sili- 

 cious earth, several feet thick. The earth consists mostly of silica, with a small per cent- 

 of iron. As the marl originated from the shells or earthy portions of mollusca, so this 

 earth has originated from the remains of animalcules. Hence the general mode of the 

 formation of both classes of deposits is the same. 



A few localities of infusorial earth have been discovered in Vermont; but probably not 

 a tithe of what may be found upon a careful examination. The account which we give is 

 compiled from the results of our predecessors, particularly the second Report on the 

 Geology of Vermont by Prof. Adams. 



"The most extensive deposit in the State is at the bottom of Hosmer's Pond in Peacham. 

 It is in the southwest corner of the town, containing from 250 to 300 acres. 

 The southwest part is from two to six feet deep. Over the greater part of 

 the bottom, generally above a deposit of peat, but sometimes resting on 

 blue clay, is the deposit of infusorial silica. When the bottom is gravelly? 

 none is seen. The peat varies in thickness below the infusorial deposit. 

 In a few places peat covers it for an inch or two, but generally a short grass 

 grows upon it. In a few places "eel-grass" is seen growing on it. The aver- 

 age thickness of the deposit is six inches. If it covers 200 acres of the 

 pond, there are not far from 1,904,000 cubic feet, or over 14,000 cords ! 

 If every cubic inch contains ten billions, the total number in this deposit 

 of animalcular shells cannot be less than 20,000,000,000,000,000." 



Fig. 79 shows the position and shape of Hosmer's Pond. That part of the pond in the s 

 figure which is dotted was alone examined, because the water was too deep in the central Hosier's Pond, 

 part to be probed by Mr. Hall's auger. 



Infusorial Forms from Hosmer's Pond, Peacham ; magnified 270 diameters. 



Fio. 80. 



Fio. 81. 



g ^ 



Fia. 82. 



Fio. 89. 



Hiiiiiii 



Fio. 83. 



Fio. 84. 



Surirella splendida. 



Eunntin i.-ti-nlnn J^unolia decaodon. 

 Pinnularia Suecica. 



Fio. 88. 

 Fl<*. 85. Fio. 86. 



o , ra ID 



w <*>* 



Pinnularia viridis. Tabcllaria trinodis. Gnillion ella distans. Himanlitlium arcus. Stnuroneis Bailcyi. 



