26 H. Goadby on making wet Preparations of Animal Substances, 
sides, in the angles of the cell, and even upon the hottest glass: 
—ultimately they coalesce and an air bubble of some size is the — 
result. For the same reason, (the displacement of air,) the prep» 
aration must be placed carefully in the cell, and if it possess — 
cavities in the under surface, they should be pressed out, if possi- 
ble, while the preparation is entering the cell; and this should be 
managed so that one end of the preparation goes into the vessel 
first, ‘and the remainder: lowered gradually.. A good steady 
stream of fluid should be poured into the cell, the preparation 
being held down by a camel’s hair pencil or forceps, until all ex- 
traneous particles be washed away, and the fluid continue bright — 
and clear. When at rest the fluid in the cell will present a com 
ver — bounded on all sides by the painting of marine glue. 
repare one surface of the cover, either by the tongue or 
brushing on the fluid as before, and holding it by a pair of for 
ceps at one end of its longest diameter, lower the other end to 
the cell, and let it down gradually—the excess of fluid running — 
before—until it be in its place; then adjust it accurately, press 
down the cover till it touch evenly every part of the bed on 
which it is to rest, remove with a brush whatever fluid may yet 
remain on the outer edges, and paint them ence more with the 
naphtha solution, including this time the top glass: apply the 
‘layer of black cement be required, allow the first to become 
quite dry, and isolate it, as before directed, with the naphtha solu- 
sé 
Drilling or cutting circular holes in glass for 
A more 
elegant mode of pe rags a cell, is by drilling a circular hole 
4. 
through a piece of glass (fig. 4); but when I 
first attempted this plan, (in the years 1839-40, ) 
the cost was prohibitory. At last I employed at 
the same time, three workmen in London to as- 
certain the lowest rate of cost at which holes of 
tity not less than one skrcies Neither of these 
men employed the same means; one of them, a German, cut 
most beautiful eee perfectly square inside, but he could not do 
ch. 
them for less than Is. 6d. or 36 cents eac 
Another made “ets iudiffnres: cells at ls. or _ cents each; i 
and the third made excellent work at 6d. or 12 cents each. 
sequent, another man undertook to do them equally re for half | 
that sum, and ultimately I procured them at the same price, eX 
cellently ‘cut, from Mr. Dennis of 1 Charles street, St. John’s 
street road, London. The following is the plan of ‘proceeding 
procure a copper tube (or drill, as it is ealled) of the diametet 
you desire your cell to bes I have aengs since | 
tion: successive layers ‘of the black cement must always be ap 
rated. : 
{ 
