330 
DIRECTIONS FOR TI1E MICROSCOPE. 
“ These capsules may be kept in the water lor several days without 
any further perceptible change. When that is dried up they return to 
the opake state, and the same operation may be several times repeated 
on them. 
“ In exhibiting this spectacle to some friends, pure water not being 
just at hand, a drop of brandy was substituted for it. This gave rise 
to a phenomenon equally curious and unexpected. The grains expand 
as in the water; hut in the mean time they are put into rapid motion, 
each grain darting from side to side with the vivacity of a swarm 
gnats in the air, As they approach to complete expansion the motion 
dies away, and one after another sinks to the bottom. By a small ad- 
dition of fresh brandy some few are excited a second time, but with 
fainter movements. Presently the liquid begins to be obscured, and in 
a few minutes the grains are mostly dispersed and decomposed, and the 
spirit exhaling, leaves a sort of extract on the glass mixed with many 
undissolved particles, among which sometimes appear a few unbroken 
grains, much changed, and now resembling an empty bladder lying 
flat/' 
Mr. Howard, after the same experiments on various other plants, 
observes, “ The proper spirit for ibis purpose seems to be a mixture ot 
one part of pure spirit of wine with two of water. A stronger spirit or 
spirit of wine alone may sometimes he required, when we operate 
upon a pollen which has by any means become previously saturated 
with moisture, (or has lost, by keeping, a part of its irritability,) but it 
does not enter the dry grain so readily as water alone. 
“ It is proper here to remark, that the utmost care is requisite to 
prevent accidental mixtures of the subjects or menstrua in these ex- 
periments, which might greatly embarrass and mislead the observer ; 
separate pieces of clear - glass for the several kinds, and separate point- 
ed glass tubes to convey the liquids, will therefore be requisite. It will 
be proper attentively to examine lire pollen dry, as well as the liquids 
before they are used, in order to be satisfied of the absence of animal- 
cules and other extraneous matter which might be suspected to in- 
fluence the appearances. 
“ I do not pretend to say that the above-related experiments were 
absolutely free from optical deception ; but I may venture to affirm, 
from frequent repetition of them, that when tried with due precaution,, 
they will scarcely ever be found to fail of producing the appearance re- 
lated.” 
MINERALS. 
Crystals . — The name Crystal is given to those polyhedral bodies, 
produced by nature and the operations of chemistry, which possess »■ 
regular geometrical form aftd rectilineal interior structure. 
