OF MICROSCOPIC OBJECTS. 30 
the edge is varnished with black or coloured rings, the 
appearance of finish is perfect. The trouble is much 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 contrawy 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 
D 
