120 On Fossil Infusoria^ discovered in Peat-earth, 



it may in some cases have been confounded with marl, from 

 which its action with acids would distinguish it. To examine for 

 the Infusoria, dilfuse a small portion in a drop of water, and exam- 

 ine with a microscope of high power. The very convenient 

 Raspail Microscope is well suited for the purpose, but to see the 

 fine Hues on these shells most distinctly, a small glass sphere made 

 according to the method of Torre of Naples, should be used with 

 the Raspail fixtures.* 



As I have not had the good fortune to obtain Ehrenberg's 

 papers on Recent and Fossil Infusoria, I am unable to give the 

 names of the species occuring at West Point. I have, however, 

 made sketches of the principal forms occuring in the peat-earth, 

 which I hope will serve to make these singular beings more gen- 

 erally known and perhaps also enable those who have Ehrenberg's 

 papers, to identify our species. All the Infusoria figured on 

 Plate 2, occur abundantly in company with the Closteria, and 

 several other forms, in ahving state, in the waters near the deposit 

 of fossils. Fig. 5, represents the species which appears most 

 abundant as a recent species, and least abundant as a fossil. 



As the species of Algse known as the Diatomse, have also a si- 

 liceous shell and occur abundantly in our ditches, &c. in a recent 

 state, and occasionally in the peat-earth in a fossil state, and as 

 this obscure but beautiful tribe appears to have been wholly neg- 



not even conjecture the origin of this sedimentary accumulation, which generally 

 occurs under circumstances which afford no clew to its source. « « * I have 

 forgotten all the localities whence the specimens were obtained, which were put 

 into my hand by various individuals some years since, some of whom supposed it to 

 be magnesia and others porcelain earth." 



* I make these spheres by drawing into a thread a portion of green glass (flint glass 

 will not answer, as the lead reduces,) and then snapping off a portion, about half a 

 line or a line in length, I lay it upon a fragment of charcoal and very carefully 

 direct upon it the flame of a blow-pipe, observing to cease to blow the moment 

 that the bit of glass has assumed the spherical form, (otherwise ashes adhere, and 

 the glass becomes full of flaws.) The spheres are then easily set in lead, thus : 

 Make a conical depression in a piece of sheet lead and perforate the apex of the 

 cone with a hole somewhat less in diameter than the glass to be set. The glass 

 is then to be forced into the hole so as to project through slightly. I have fre- 

 quently made, and set in five minutes, spheres in this manner, which would 

 magnify from one hundred, to four or five hundred times the diameter of the object. 

 Such glasses are much superior to any usually kept for sale in this country. I pre- 

 sume that these glasses would have been more used, had they been tried with the 

 proper arrangements for light. With the beautiful fixtures of the Raspail Micro- 

 scope they leave little to be wished for, either with regard to power or the dis- 

 tinctness of vision. 



