Smith^ on a Slide-holder fo7^ the microscope. 101 
holder^ the lower one [a) has three small projections on its 
inner margin, which being doubled over the inner edge of 
ring B (as indicated by the dotted points) form at once the 
means of attachment and rotation. The second or upper 
ring {c) is brought into its proper place, over, and lightly 
touching the first by bending the middle piece [b], which 
makes a sort of spring hinge, keeping the rings together, and 
retaining by its pressure the object in its place between them ; 
D, the secondary holder for very small objects, consists of a 
flat piece of metal of sufficient length to be conveniently held 
by the rings forming the clip ; in the centre of this flat piece 
a small watch spring joint [b) is fixed, the object being 
secured between this point and the projecting portion in the 
centre of the piece itself. 
When a leaf or other such large object is to be examined it 
is placed between the rings, which by their tendency to come 
together hold it with sufficient firmness, and at the same time 
without injuring the specimen; and it can then be rotated 
upon its own centre by pushing the projecting portion forming 
the spring hinge, or the two small pieces [d d). The other 
rotation is of course efi'ected by turning the milled head at 
the end of the stem ; bringing the leaf examination at any 
desired angle with respect to the object-glass, while a half 
turn brings the underside into view without the necessity of 
disturbing the object itself; this facility of examination, 
which is given by the ring-like form of the instrument^ will 
be found of some little value. 
With respect to the size of the rings forming the clip, I 
may say that although in my own instrument they are about 
one inch in diameter, yet I think they might with advantage 
be made somewhat smaller; but as this is very much a matter 
of convenience^ no precise size need be given. 
On a Revolving Slide-holder for the Microscope, combined 
with Selenite Stage. 
The accompanying diagrams show a very simple addition to 
the accessory apparatus of the microscope, which I would 
term a revolving slide-holder, and which will, I think, be 
found of use with some of the simple forms of microscopes. 
It consists (as will be seen in the drawings) of an upper plate, 
a, about 3 in. by 1, with two clips for holding the slide, a 
secondary one upon which the top plate revolves, an inter- 
mediate space (b a)j and a lower plate somewhat larger and 
