EDWARDS, ON FINDERS. 
201 
by his countrymen,, than it will be by the lovers of science 
in Europe."^ 
In the report of the committee of the Microscopical 
Society, appointed to consider the subject of an efficient 
finder for the microscope, the following properties were con- 
sidered essential : — First. It should be applicable to any 
microscope, whether furnished with stage movements or not ; 
and it should not preclude the use of those movements. 
Second, It should not require new labels to be placed on the 
slides, or any mark or index to be made upon them. Third. 
It should not be necessary to remove the slide or finder for 
the registering or finding of every separate object. Fourth. 
The divisions on the index should be easily read. Fifth, It 
should allow the microscope to be used in the inclined posi- 
tion ; and — Siwth. It should be cheap, and simple enough to 
be constructed by any one possessing a moderate amount of 
mechanical skill." 
The first of two instruments which I am about to describe 
fulfils all of these requirements, if we except, perhaps, that 
one which says it should be so simple that it might be made 
by the microscopist himself. It is true that mine could 
really be so made ; but when we wish for exactness in gra- 
duation in an instrument of this kind, it is best to have it 
so graduated by a proper workman ; and I have had mine 
engraved, so that I might have as many impressions as I 
should need, all alike in the essential point of correct 
graduation. 
As the slides mostly in use are those of the dimensions 
recommended by the Microscopical Society (of three inches 
by one), I have had my indicator made to that size; though, 
of course, as will be seen from the description, it could be of 
any dimensions. 
Before describing the indicator itself, I shall speak of the 
preparation of the microscope necessary for its use. 
The stage is ruled with two lines across it, intersecting 
each other exactly in the centre of the field of vision ; and 
in the case of those microscopes having mechanical stages, 
these lines are continued across a circular piece of glass, 
which is made to fit into the hole in the stage, and the point 
where they cut each other is always brought into the centre 
* Professor Bailey has bequeathed to the Boston (U.S.) Society of Na- 
tural History his whole microscopical collection, contained in books, with 
an index-volume, his collection of Algae, his rough material for microscope 
research, including his cabinet of minute fossil animal and vegetable forms 
together with his microscopic memoranda and unpublished papers, and his 
very valuable library of microscopic and botanical works. 
