1819.] Description of an improved Microscope. 5g 
would be very useful for dissecting insects, as it shows the image 
erect like a smgle lens ; its power is about 60 (common compu- 
tation), nor will it magnify above that with distinctness ; it is 
composed of seven lenses, and, nevertheless, shows the object 
very clear and distinct ; its body is 104 inches long; it is in its 
principle the eye-piece of a small telescope, connected with the 
field and double eye-glass of the common compound microscope ; 
the little eye-piece at the bottom is 36 inches long; as I have 
it, a body of this nature is made to screw into the arm of the 
instrument like the other ; but in this state it is not sufficiently 
steady to be used with comfort, as a very slight tremor is per- 
ceptible when you are working. I recommend a stand for it, 
such as that in fig. 3, made very solid, with a rack and pinion to 
move the body hike that in Culpepper’s microscope. 
The advantages of this instrument would be that, being to be 
used for a continuance, it would not strain the eye like a single 
lens of the same magnifying power, which would need to be 1th 
of an inch focus; that there would be abundance of room to 
manage the dissecting instruments, as the focal distance of this 
microscope from the object is half an inch; and that the operator 
would not be under the necessity of putting his nose close 
down over the object, and thereby darkening it, so that the light 
would require to be thrown up from below and reflected back 
upon the object by a silver cup. 
I do not see any particular utility in this last instrument, 
except as a dissecting microscope. I have now given a plain 
account of this instrument without any reference to theory, or 
any display of algebra and mathematics. I have written for the 
ractical man only, to whom I recommend the instrument as a 
valuable article of his trade, the cost of which will not exceed 
that of a good compound microscope of the common make, with 
a transparent and opaque solar apparatus, and will, I think, give 
much more satisfaction ; at least, to those who can distinguish a 
bright, clear, achromatic, distinct image, from a distorted, dull, 
confused one, and who prefer in a solar microscope an image 
abundantly magnified, and as sharp as a miniature picture, to a 
huge, indistinct shadow. It is the established practice of every 
imventor to extol the merit of his own production, and to decry 
all others ; but I do not think I have asserted any thing here of 
mine which will not bear the closest examination by those most 
skilled in optical instruments. 
