( 135 ) 
AiiT. XXV . — Account an Impromd Catoptrlcal Micro- 
scope^ by Professor Amici o^* Modena. Translated from 
Gilbert’s Annalen 
IVIiciioscoPEs constructed on catoptrlcal principles, have 
been known since the time of Newton ; but in consequence of 
their imperfection, and the great improvements made upon the 
dioptrical instruments, they have been, of late, almost entirely 
neglected. 
Some years ago, an eminent natural philosopher. Professor 
Amici of Modena, constructed a very excellent catoptrlcal mi- 
croscope, in which he seems to have avoided the imper- 
fections to which the instruments formerly constructed upon 
the same principle were liable, and to have eomibined several ad- 
vantages which are not possessed by the best dioptrical micro- 
scopes now in use. The ingenious inventor has lately published 
a minute description of this improved instrument, in a memoir 
inserted in the 18th volume of the Transactions of the Italian 
Society. 
The body of this microscope consists of a hofizont^ brass 
tube, 12 inches in length, and Ij^gth in diameter. At one end 
of the tube is placed a concave speculum of metal, whose axis 
coincides with that of the tube, and whose superficies is ellip- 
tical, and so calculated, that of the two foci, the one falls at 
the distance of 2/^th, and the other at 12 inches from its 
centre. A small arm within the tube, carries a small plain mir- 
ror of metal of an oval form, placed at the distance of 1^-^^ indies 
from the former, opposite to it in an oblique direction, and sup- 
ported by an oblique section of a metal cylinder /^th of an inch 
in diameter. The centre of the polished surface of this mirror 
coincides with the axis of the concave mirror, which is situa- 
ted at the distance of 1 inches from the centre of the other. 
This plain mirror is so placed, that, while it receives the 
image of the object (which is placed on a moveable object-bearer 
attached to the pillar below it) by means of a small aperture in 
* In vol. i. p. 214. we have given a notice respecting this microscope, commu- 
nicated to us by His Royal Highness the Archduke Maximilian, who, we under- 
stand, has recently presented one of the instruments tp the Imperial Cabinet of Na- 
tural History at Vienna. — E b. 
