The three firft compound microfcopes that attract our notice,
are thofe of Dr. Hooke, Euftachio Divini, and Philip Bonnani.
Dr. Hooke gives an account o f his in the preface to his Micrographia,
which was publifhed in the year 1656; it was about
three inches in diameter, feven long, and furnilhed with four
draw-out tubes, by which it might be lengthened as occafion required
: it had three glalfes, a fmall objeft glafs, a middle glafs,
and a deep eye glafs : Dr. Hooke ufed all the glalfes when he
wanted to take in a conliderable part of an objeft at once, as by
the middle glafs a number o f radiating pencils were conveyed to
the eye, which would otherwife have been loft: but when he
wanted to examine with accuracy the fmall parts o f any fubftance,
he took out the ihiddle glafs, and only made ufe of the eye and
objeft lenfes ; for the fewer the refraftions are, the clearer and
more bright the object appears.
An account o f Euftachio Divini’s microfcope was read at the
Royal Society; in 1668. * It conlifted o f an objeft lens, a middle
glafs, and two eye glalfes, which were piano convex lenfes,
and were placed fo that they touched each other in the center o f
their convex furfaces; by which means the glafs takes in more of
an objeft, the field is larger, the extremities o f it lefs curved,
and the magnifying power greater. The tube, in which the
glalfes were inclofed,- was as large as a man’s leg, and the eye
glalfes as broad as the palm o f the hand. It had four feveral
lengths ; when Ihut up, it was fixteen inches long, and magnified
the diameter of an object forty-one times ; at the fecond length,
ninety times; at the third length, one hundred and eleven times;
‘at
* Philof. Tranf. No. 42.
at the fourth length, one hundred and forty-three times. It does
not appear that E. Divini varied the objeH lenfes.
Philip Bonnani publifhed an account o f his two microfcopes in
1698; * both were compound; the firft was limilar to that which
Mr. Martin publifhed as new, in his Micrographia Nova,f in
1712.. His fecond was like, the former, compofed o f three
glafles one for the eye, a middle glafs, and an objeft lens:
* they were mounted in a cylindrical tube, which was placed in an
horizontal pofition; behind the ftage was a fmall tube, with a
convex lens at each end; beyond this was a lamp ; the whole capable
o f various adjuftments, and regulated by a pinion and rack;
the fmall tube was ufed to condenfe the light on the objeft, and
fpread it uniformly over it according to it’s nature, and the mag-
nifying power that was ufed.
I f the reader attentively confiders the conftruction of the foregoing
microfcopes, and compares them with more modern ones,
he will be led to think with me, that the compound microfcope
has received very little improvement fince the time of Bonnani.
Taken feparately, the foregoing conftruaions are equal to feme
of the moll famed modern microfcopes. I f their advantages are
combined, they are far fuperior to that of M. Dellebarre, not-
withftanding the pompous eulogium affixed thereto by Meii. He
L ’Academie Royale des Sciences. J
* q ' From
* Bonnani Obfervationes circa viventia, &c.
4 Micrographia Nova, by B. Martin, 4^0, ,
j Memoires fur les Differences de la Conflruäion et des Effets dn Microfcope,
de M. L. F. Dellebarre, 1777.