Again, it has been said, that by giving the motions and
adjustments to the optical part, it is rendered much less
steady than it might be under other circumstances ; that
it is like moimting a telescope on a mop-stick ; that
immobility is of most virtual importance for observa-
tion, &c. I answer, that by making the work sufficiently
strong and solidy and the optical part no larger or longer
than is necessary, the instrument is rendered abundantly
steady, and free from tremor even with its highest powers.
M



162 MICROSCOPIC ILLUSTRATIONS.
At the same time I willingly admit, that if the body is
made very long or large it will be almost impossible to
combine the stability requisite for practical purposes
with a capability of traversing and adjustment.
