106 THE MICROSCOPE. 
spring, creek, river, and swamp waters, and water-plant sources; 
these were alternately cleaned and spread upon slides, and there- 
from its quota of leading species were selected by the aid of a very 
fine bristle, and transferred to separate bits of thin cover-glass. 
When all the material available at the time had been thus gone over, a 
thin cover-glass was selected and upon this all of the selected forms 
were transferred by the methods and means described in the article 
on arranging diatoms. It can be readily surmised, that in the pur- 
suance of this work, many features connected with the structure and 
colors of particular diatoms would be observed; for example, the 
fragile nature of many of the discs, the hoop, or connecting band, 
easily separating from its disc-like sides; many of the navicular 
forms separating in like manner; the flexible, or elastic nature of 
the nitzschias ; many of the discs which show beautiful tints when 
in balsam, merely appearing of an amber brown while dry; also, 
may be noted the wide variation in size, in diameter, or otherwise, of 
the same species ; as well as the variety in contour, or outline, of 
similar species ; which facts impress themselves upon the mind with 
more effect than when an ordinary spread slide is being passed under 
observation. I hope to be able at some future time to review all of 
the strewn and type-plate preparations which I, and others, have pre- 
pared, and which I hold, of Mobile, Ala., diatoms and have them iden- 
tified and listed, so as to carry the list of species noted to the highest 
figure yet reached forthis epoch. As numerous familiar species were 
not available in the crude state, when the present type-slide was being 
prepared, they will therefore not be alluded to in this article. Since 
I undertook to make the above initial type-plate I have found that 
the method is rapidly applicable to the analysis of all diatom-bearing 
material, as within an interval of an hour or two at most, a repre- 
sentative slide of a hundred or more of the various contained species 
in a given material may be prepared, suitable to the most fastidious 
inspection ; by adopting the system of freehand selecting, the slow 
system of referring to species in strewn mounts by the record indices 
of the Maltwood finder, would be largely dispensed with, and other 
advantages become manifest after a little reflection. As an illustra- 
tion of the ease and quickness of the selecting methods previously 
published, and followed out by myself, I may state that I have pre- 
sented to interested parties seven selected slides of different fossil 
earths, no preparation containing less than fifty diatoms, or foram- 
inifera, the limit being about one hundred. I would, however, not 
pretend that they were prepared in the highest perfection of the art. 
The following list of species, identified through the kindness of 
