DESCRIPTION OF THE ACHROMATIC MICROSCOPK. 91 



microscope has been made with Dr. Goring's joint, 

 fifty have with mine. 



Fig. 16. 



Fig. 15 represents a pair of forceps and a pin- holder, 

 attached to a ball-and socket joint ; the stem, e, fits into 

 holes formed in the stage to receive it. Opaque objects, 

 when mounted on a circular disc with a pin, are held 

 more firmly by the pin- holder (as seen by the figure) than 

 by the forceps. It is preferable, also, when the instru- 

 ment is on a small scale, to that ingenious contrivance in 

 Dr. Goring's Engiscope (see plate, fig. 23), as it admits 

 of the forceps being made smaller. 



The arm, fig. 16, is used for carrying the forceps when 

 the stage is removed. The pin, b, fits into one of the holes 

 in the block of the instrument; and the pin, c, fig. 15, 

 into the hole, a. This arrangement for viewing opaque 

 objects allows large silver cups to be used, for conden- 

 sing the light upon them. This could not be done, if 

 the stage did not take off, unless the aperture in it were 

 immoderately large. 



The method of viewing opaque objects by means of 

 silver concave reflectors, is by far the simplest and the 

 readiest; and when these are of considerable diameter 

 and of proper curvature, we not only obtain the central 

 illumination, but also that beautiful play of light and 

 shade afforded by the oblique pencils. 



For investigating insects, or other objects not mounted 



