1819.] Description of an improved Microscope. 55 
generally nearly flat, can be seen with a high power to greater 
advantage ; but I am no advocate for microscopes of high powers. 
I think as much may be seen with a power of about 60 diame- 
ters (rating the standard of sight at eight inches) as can be seen 
with any power whatever; at least, | am sure this is the case 
with opaque objects. Besides, the field of view in the common 
microscope is larger than in mine, which, with transparent 
objects, is of importance, as a large portion of the object can be 
in the focus: with opaque ones again, as but a small portion can 
be seen at a time, it is of little consequence whether the field is 
large or not. The field and double eye-glass in the transparent 
microscope serve as the lowest magnifiers in the opaque one, and 
instead of the common astronomical eye-pieces for obtaining the 
higher powers, double eye-glasses might be used which would 
give a larger field, but it is not worth while. Though, cetervs 
paribus, the opaque microscope has much more light than the 
transparent one, still in the latter there is abundance of light for 
send transparent objects, which are best seen in a weak 
ight. 
"i now proceed to the way of managing the solar apparatus, 
Fix the instrument upon its box, as in fig. 2; orif opaque objects 
are to be examined, mount it as in fig. 1, turned upside down. 
Choose a room where the sun-beams fall on the floor; place a 
common dressing-glass there, as. ¢, fig.2. Then place the instru- 
ment upon a table, so that its side may be opposite the window, 
but not where the sun-beams fall ; reflect the light from the dress- 
ing-glass, ¢, to the great mirror, N, so that you may see its 
shadow on the wall. When you have done this, the instrument 
is managed just as if you were looking through it, by only 
reflecting the light downwards. The image appears at the 
bottom of the box, 7; » is a piece of box wood 54 inches dia- 
meter, covered with vellum paper; its surface is curved, so that 
the image may be received upon it quite perfect. is a piece of 
pasteboard blacked, with a round hole 52 inches diameter, a 
sheet of paper being placed under it. The end of the camera, 
8, being removed, and the cloth, 7, attached to the lid of the 
camera, t, the image may be drawn on paper with the utmost 
ease. This cloth has a hole in it, as represented in the plate ; it 
is stiffened round the edges with an iron wire, and just suits the 
face, so that when it is used, all foreign rays are excluded from 
the camera ; but when two people are looking into it at once, it 
is not needed, as their heads exclude the light sufficiently. 
There is nothing peculiar in the rest of the apparatus attending 
this microscope ; so I shall say nothing about it, except T (fig. 
1), which is a small instrument made like a little vice, but very 
slight, and fixes into one of the holes in the stage ; it is very 
handy for seizing many opaque objects ; for example, laying hold 
of the pin by which colleciiens of insects are fixed in their boxes, 
and exhibiting the insect without any damage in any direction. 
