136 SWAMMERDAM'S CHIEF SECRET.

very slow vertical motion, by which means the
operator could readily alter their height, as he
saw most convenient to his purpose. The office
of one of these arms was to hold the little
corpuscule, and that of the other to apply the
microscope. His microscopes were of various
sizes and curvatures—his microscopical glasses
being of various diameters and focusses, and,
from the least to the greatest, the best that
could be procured in regard to the exactness of
the workmanship and the transparency of the
substance.

His way was to begin his surveys with the
smallest magnifiers, and from thence to proceed by
degrees to the greatest; and by nature and use he
was so Incomparably dexterous in the inanagement
of them, that he made every observation subser-
vient to the next, and all tend to confirm each
other and complete the description. But the con-
structing of very fine scissors, and giving them an
extreme sharpness, seems to have been his chief
secret. ‘hese he made use of to cut very minute
objects, because they dissected them equably,
whereas knives and lancets, let them be ever go
fine and sharp, are apt to injure delicate substances.
His knives, lancets, and styles, were so very fine,
that he could not see to sharp them without the
aid of the microscope; but with them he could