206 PBEPARATION 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, 01 

 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 source 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 Handbook, 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,- 



