206 PREPARATION AND MOUNTING 
“The negative intended to be reduced is then arranged 
vertically, with its centre in the axis of the microscopic 
body, at a distance from two to four feet from the lower 
object-glass, and with a convenient screen of card, wood, or 
thick paper, to cut off any extraneous light that would 
otherwise pass beyond the limits of the picture. 
“A small camphine-lamp is employed for the purpose of 
illuminating the negative, having a good bull’s-eye lens as 
a condenser, so arranged with its flat side next the lamp 
that the refracted rays shall just fill the whole of a double 
convex lens of about six inches in diameter, the latter being 
placed in such a position as to refract the rays of light in a 
parallel direction upon the negative. By this arrangement 
the bull’s-eye lens of about two inches and a half in 
diameter appears as the scurce of the light instead of the 
small flame of the lamp. 
“ By using a bat’s-wing gas-burner of a good size, a single 
lens, instead of the two, may be so placed as to give the 
necessary uniformity of illumination.” 
This arrangement requires the same care in working as 
that before mentioned, the pictures being produced, de- 
veloped, and fixed by the same treatment. 
It is certain that almost every manipulator makes some 
small changes in the method of producing these minute pic- 
tures; but the rules given, though far from new, are — 
sufficient for all purposes; and I may say with truth, that 
those which I procured when these wonders were quite new, 
are fully equal in every respect to the best usually met with 
at the present time. 
With these instructions I shall close my Handbouk as I 
believe that nearly every branch of the Preparation and 
Mounting of Microscopic Objects has been treated of. Not 
that the beginner can expect that he has only to read this 
to be able to mount everything; but that there are difficul- 
ties from which he may be freed by instruction, when other- 
wise he would have been compelled to learn by failure alone. 
[ may here, however, repeat certain advice before given,— 
