58 THE NORTHERN MICROSCOPIST. 
it becomes clean. If, on examination with the microscope, it is 
found there is much flocculent matter besides the diatoms and 
sand, it can be removed by boiling for a few seconds in caustic 
potash, and then turning a/most instantly into plenty of soft water 
to destroy the action of potash. The diatoms are chemically free 
from all organic matter, and they may be dried and kept in small 
phials in powder, or be put into equal parts of alcohol and water, 
and kept for future separation from sand and other inorganic matter, 
or we can proceed at once to isolate the diatoms, also to separate 
into sizes. To do this, put the cleaned diatoms into a small bottle, 
fill with soft water, filtered, and after shaking thoroughly turn off 
all that floats after five seconds into a larger bottle. Repeat the 
process, and after some five or six repetitions we shall find very 
little but sand in the first bottle, which we will throw away unless 
some very large diatoms remain, which can be removed by drying 
on a slide and picking with a mechanical finger. As soon as the 
material in the large bottle has settled, turn off the water and return 
the material to the small bottle and repeat the process, allowing 
longer time to settle. This process may be repeated five or six 
times, or as many times as necessary to make the separation satis- 
factory, allowing more time on each repetition to settle. Another 
excellent method is used by Christian Febiger, of Wilmington, 
Del., whose arranged slides have attracted much attention. Strain 
through No. 18 bolting cloth to obtain large diatoms. The 
remaining small diatoms and sand must be placed in a clock 
crystal and rotated. The sand will go to the bottom and the 
diatoms can be poured off repeatedly until clean as desired. 
It will be impossible to save all the diatoms in the repeated 
washings. So long as 100 slides can be mounted from a mass not 
so large as a small pea, be content to save time and patience by 
losing a tithe of the harvest. Do not be disappointed when you 
find hardly enough diatoms remaining to make a fair thickness of 
carpet in your phial, for if clean you will have sufficient for yourself 
and for several of your friends, even then. 
For mounting, always place with a pipette a drop of the fluid 
containing them upon the cover glass, and never on the slide. 
Prof. Hamilton L. Smith was my teacher in this method, and I 
know of no other equal to it. Cut a piece of photographer’s tintype 
into strips about one inch wide and three inches long, then cut 
away all except enough for a handle, leaving one inch square on 
one end. Bend the end of this handle and fasten into a cork in a 
bottle, which will serve for a holder. Upon this plate place the 
clean cover, and by means of a pipette drop a little of the dilute 
alcohol and diatoms upon it, and apply a gentle heat with a spirit 
lamp. The alcohol takes fire and burns off. The remaining 
alcohol causes the diatoms to become evenly distributed. If in- 
