48 
GEOLOGY OF THE FIRST DISTRICT. 
INFUSORIA. 
These microscopic animals inhabit the waters of streams, and of salt and fresh water ponds 
and marshes. In many places they have left masses of their remains, that have accumulated in 
course of time, so as to form important geological deposits. It is but a few years since it 
was first known that these minute animals composed the mass of the white pulverulent earth 
so common in the bottom of pond-holes and marshes, in which water stagnates during the 
warm season of the year. I first became acquainted with this material, while making a geo¬ 
logical survey of New-London and Windham counties in Connecticut, in 1831. It had been 
used for many years as a polishing powder, to polish brass, silver, etc., and had been packed 
in small parcels and sold for that purpose in the country around. I supposed it to be lake 
marl, until an acid was applied, and found that it would not effervesce; and on making an 
examination, found it to be siliceous. I did not then know that it was secreted by animals to 
form their coverings, but supposed it to be derived from the decomposition of the surrounding 
primary rocks. 
The discoveries of Ehrenberg have led to investigations in various parts of the world, and 
very numerous localities of this infusorial earth are now known in New-England, New-York, 
and some in other states. This earth, so far as my observations have gone, leads to the con¬ 
clusion that it is found more abundantly in primary regions than in others. Many of the bog 
meadows and stagnant ponds in the Highlands contain it. Prof. J. W. Bailey, my successor 
as instructor of mineralogy and geology in the United States Military Academy at West-Point, 
has investigated the subject of fossil infusoria with much zeal and success. He has had the 
kindness to furnish me with the following results of M. Ehrenberg’s examination of some fossil 
infusoria sent him by Professors Silliman, Hitchcock and Bailey, and Prof. B. has added 
remarks of his own. 
Ehrenberg, on the 25th March, 1841, made a communication to the Berlin Academy, 
giving results of his examination of American Fossil Infusoria received from Profs. Silliman, 
Hitchcock and Bailey. He states, 
1. That in North and South America occur not only living but fossil microscopic organisms, 
geologically important in thickness and extent, and very similar in their relations to the 
European. 
2. The American forms are for the most part similar to the European. 
3. One hundred and forty-three American species are common to Europe, and seventy-one, 
or one-third, peculiar to America. 
