WILLIAMS;, on the Martin Microscope. 37 
Here is a circular glass plate with five hollows for larger 
objects. It fits into the clip of the stage_, and as the plate 
revolves on its centre^ the hollows can be brought in succession 
under the microscope. For still larger objects this semicircular 
glass plate, having three similar hollows, can be applied in 
like manner. 
There are also live boxes of large size that can be applied 
to the stage, but they ofier nothing peculiar in their con- 
struction. 
I have now to direct your attention to a rather singular 
arrangement, which I have never met with before, although 
it is possible some gentlemen present may be acquainted with 
it. It is a peculiar apparatus for exhibiting large opaque 
objects, such as minerals for instance, and as it can be used 
with the lower powers only, whose focus is beyond the reach 
of the stage in its present position, a provision has been 
made for its application, which is not at first sight very ap- 
parent. One portion of it consists of a ball turning in a 
socket, with another socket in it for receiving the other parts 
of the apparatus. In order to apply this we must turn the 
stage upside down, and thus we are enabled to lower it 
several inches. We can now screw the ball and socket 
on to the stage. Before doing this I will introduce to you 
these triangular forceps, the lower parts of which fit into the 
stage in its present inverted position. These forceps are calcu- 
lated to hold objects of moderate size only. When it is required 
to view larger objects, the ball and socket must be screwed on 
to the stage, and the instrument now before you applied. It 
consists of two forks, as they may be called, opposed to each 
other, each having three points, and adjustable to any dis- 
tance within the range of the instrument. An object being 
placed between these, the forks can be firmly secured in the 
required position by means of binding screws at the top 
of each. The lower part of this instrument being inserted 
into the socket in the ball, it can be readily turned in any 
direction, and the object examined in the most favorable 
position. For another class of large objects the brass pan 
having three opposing screws now before you is available. 
These enable the object to be firmly held, when the pan can 
be fixed into the socket in the ball, and the objects viewed 
in any position. 
But it may be required to examine objects too large to be 
brought into the focus of the lower powers, even with this 
arrangement ; Martin has even provided for this contingency. 
Here is a long arm to which the ordinary stage can be 
attached, as, by loosening a screw with a miUed head, the stage 
