1897.J MICROSCOPICAL JOURNAL. 177 



toins leaving the larger and coarser portions to the rear. 

 By this means enough diatoms may be secured for a trial 

 study of five or more slides from a very small piece. 



This simple process is susceptible of great refinement 

 when properly done. It is the most expeditions way in 

 which to get acquainted with the characters of the depos- 

 it; whereas, if the process does not give satisfactory re- 

 sqltsat the hands of anyone trying it, the customary 

 process of boiling in alkaline, or acid solutions would have 

 to be resorted to. More time is thus consumed and it 

 will scarcely remove the amorphous clay particles which 

 are apt to interfere with a good concentration. I deem 

 the suggestions given herein as pertinent, as the deposit 

 belongs to the category of deposits seldom available, and 

 thus involves experimental tentative processes for its 

 mastery. 



The deposit offers a problem to the chemist, viz : to 

 find an acid or combination of acids which will promptly 

 dissolve the compound mineral which has metamorphosed 

 the internal chambers or casts left by the Foraminifera. 

 These shell casts seem to be proof against four of the 

 commoner reagent acids. This problem offers a fine ex- 

 perimental field in the line of micro-chemistry. 



If a simple water cleaned slide of the diatoms is placed 

 under the microscope using a 1 inch or a | inch objective 

 remarkable chemical phenomena may be observed. By 

 depositing a drop of sulphuric acid on the slide, and then 

 adding a drop of muriatic acid, every foraminiferal form 

 will be violently attacked and torrents of gas bubbles 

 will be thrown off in streams until the internal casts 

 within the foraijiinifera are exposed. Then the power 

 of the acids is at an end. In the meantime the diatoms 

 will have been materially brightened, revealing the 

 sculptural markings more clearly, where not masked by 

 pyrites. The action of the nitric acid in dissolving the 

 iron mineral does not present any phenomenon of inter- 



