OF MICROSCOPIC OBJECTS. 33 



the edge is varnished with black or coloured rings, the 

 appearance of finish is perfect. The trouble is ranch less 

 than with most of the other methods, and the illumination 

 of the object very slightly impaired. 



To varnish the edges of these covers, make circles of any 

 liquid upon the glass slide, and perform any other circular 

 work mentioned hereafter, the little instrument known as 

 " Shadbolt's turntable " is almost indispensable. It is made 

 as follows : At one end of a small piece of hard wood is 

 fixed an iron pivot about one-eighth inch thick, projecting 

 half an inch from the wood, which serves as a centre upon 

 which a round brass table three inches in diameter revolves. 

 On the surface of this are two springs, about one and a half- 

 inch apart, under which the slide is forced and so kept in 

 position, whilst the central part is left open to be worked 

 upon. The centre is marked, and two circles half an inch 

 and one inch in diameter are usually deeply engraved upon 

 the table to serve as guides in placing the slide, that the 

 ring may be drawn in the right position. When the slide 

 is placed upon the table underneath the springs, a camel- 

 hair pencil is filled with the varnish, or other medium used, 

 and applied to the surface of the glass ; the table is then, 

 made to revolve, and a circle is consequently produced, the 

 diameter of which it is easy to regulate. Mr. Hislop places 

 two equidistant pins at opposite sides of the centre of 

 the revolving plate, against which the opposing edges of 

 the slip are made to bear, so that the instrument is self- 

 centering. The springs are turned in contrary directions and 

 are screwed on the pins, or the screws are made into the 

 pins against which the sides of the slide bear. 



The form of this " turntable " has been modified by many 

 manipulators to suit their several wants. Almost all slides 

 used are of nearly the same size 3 in. by 1 in. ; and therefore 

 the centres of all are equidistant from the edge. On this 

 account one of my friends has a thin brass bar screwed upon 

 the side of his turntable in such a position that the centres 

 of the slides and table always coincide. The rings of varnish 



