EDWARDS, ON FINDERS. 
205 
top to bottom, and the bottom strip (as b in the fig.) is also 
reserved for the same purpose, in which they run from right 
to left. 
rig. 4. 
When the slide is placed on the stage it rests against this 
ivory scale and the brass guide-strip, so that it coincides 
exactly with that of the field of vision. A strip of brass is 
now bent into the form seen in the figure, c, and fastened 
at one end to the fixed stage on which the other moves, at o. 
The other end is brought to a fine point, and is blackened, 
so that it can be easily seen upon the ivory registrar. This 
strip or pointer is so arranged that when the moveable stage 
is brought perfectly square with the fixed one, its point rests 
at 50 in the upper zero line. 
From an examination of the figures, it will be at once seen 
that, as the stage is moved in any direction, the registrar 
moves under the point, and when we find an object which we 
wish to register, we look at the pointer and observe the lines 
it points to, and write them down in the form of a vulgar 
fraction, i. e., the numbers on the scale «, above the line, and 
those on h below."^ 
This registrar will be found to be of use on searching a 
slide for the first time, as we can begin at zero and travel 
across to 10 ; then, falling one or two graduations, we return 
across the scale, noticing the object by the way, and in this 
manner we traverse the whole portion of the slide upon which 
the objects are placed. 
This instrument will not be of so extensive an application 
as the one first described, but still it would be found useful 
when attached to microscopes having mechanical stages. 
* I should perhaps mention that I have found the best substance for 
attaching the paper indicator to glass slides to be the so-called " mucilage" 
sold at stationers' shops. 
