110 MICEOSCOPES FOE 



Section IX. — On Infusoria contained in Flints and Semi- Opals. — 

 It is hardly possible to take up and examine a dozen flints without 

 discoveiing species of Infosoria inclosed within them. These may 

 be best seen imder the microscope, when very thin sections are made, 

 like those of fossil woods, teeth, coal, &c. : when these are polished 

 and cemented on glass slides, they form permanent objects. Small 

 splinters of flint, broken ofi", may be used for investigation by the 

 microscope, but such experiments are attended with veiy consider- 

 able danger to the object-glass of the instrument, by its being brought 

 accidentally into contact with their sharp edges, which oftentimes 

 cut and injure it without your being immediately aware of the fact. 



Section X. — To prepare Fossil Infusoria for the Microscope. — 

 Among various earths, marls, and chalk, will often be found the 

 siHceous shells of Bacillaria. Sometimes the whole mass consists of 

 them ; in the latter case it will be sufficient to place upon the slides 

 a little of the powder, add a drop of water, and cover it with a thin 

 plate of glass when your object is ready for the microscope. This, 

 however, will be only a temporary preparation. "When requii'ed to 

 be permanent, Canada balsam, varnish, or gum, must be substituted 

 for the water. By far the majority of specimens of shells of In- 

 fusoria are met with among foreign matters, from which it is neces- 

 eary to separate them as in the case of Guano, &c. 



"When the earth can be separated by washing in water, this plan 

 may be adopted. In some cases it requires boiling in nitric acid, 

 which dissolves the foreign matter and allows the shells to be sepa- 

 rated. In this way some care is required, otherwise the shells will 

 burst asunder, and you will only obtain fragments. Another objec- 

 tion to the use of acids, is that the shells will attract moisture when 

 required to be mounted dry. 



Another method of separating Fossil Infusoria fi'om the earths, is 

 similar to that employed by D'Orbigny in separating the beautiful mi- 

 croscopic shells of the Foraminifera, and has been successfully adopted 

 by Professor Bailey of New York, in detecting the shells of Bacillaria 

 in sedimentary deposits. It is as follows : Take the sediment or 

 earth in which Infusiora are supposed to exist, and gradually, 

 but completely dry it ; then take a glass full of cold water and 

 strew the powder upon the siuface of the water, when in a few 



