optics. 283 



circle H, passes through the hole which is towards 

 the bottom of the pillar A. B, the stage on which 

 the objects are to be placed ; it fits into a small 

 dove-tailed arm which is at the upper end of the 

 pillar, A. C, a plane glass with a small piece of 

 black silk stuck on it. This glass is fitted to a 

 groove made in the stage B j a pair of nippers is 

 fixed to the hole of the stage a, by the pin K ; the 

 steel wire of these nippers, slides backwards and 

 forwards in the socket ; and this socket is move- 

 able upwards and downwards, by means of the 

 joint, so that the position of the object may be 

 varied at pleasure. The object maybe fixed in the 

 nippers, or stuck on the point. 



To use this microscope, begin by screwing the 

 pillar A to the cover ; pass the pin R, of the semi- 

 circle which carries the mirror through the hole, 

 that is near the bottom of the pillar A ; push up 

 the stage into the dove-tail at B; slide the pin into 

 the pillar ; then pass the bar E, through the socket 

 X, which is at the top of the pin D, and screw one 

 of the magnifying lenses into the ring at F. Now 

 place the object either on the stage, or in the 

 nippers, L, and, in such a manner, that it may be as 

 nearly as possible over the centre of the stage ; 

 bring the speculum F over the part you mean to 

 observe ; then get as much light on the speculum 

 as you can, by means of the mirror, I. The light 

 received on the speculum is reflected by it on the 

 object. The distance of the lens F from the 

 object is regulated by moving the pin D up and 

 down, until a distinct view of it be obtained. The 

 rule usually observed is, to place the lens beyond 

 its focal distance from the object, and then gra- 

 dually slide it down, until the object appear sharp 

 and well defined. The adjustment of the lenses 



