268 THE MICROSCOPE. 
The other model, the first as regards the invention, is Mr. 
George Wale’s “ New Working Microscope.” It differs from the 
foregoing inasmuch as the foot and pillars are of iron, the pillars 
higher, the parts on each side being cast together so that they 
form two separable portions held by a screw. The grooves on 
the arm and the tongues on the pillars are essentially the same 
and have the same action as in the “American Concentric Micro- 
scope.” In both the advantage claimed is that the centre of gravity 
remains at about the same point with any inclination of the 
body, while in the ordinary stands it changes more or less with 
the changing angle, and the stability of the former is said to be 
increased. The idea embodied is an excellent one, and the 
instruments are as valuable for useful working stands as any on 
the market. The form, especially of the “American Concentric ” 
model, seems odd and unattractive, probably because it is un- 
common, and this, in addition to its price, may have militated 
against it. Mr. Wale’s stand is built of cheaper material in part 
and on different lines, but it is probably as desirable for the 
amateur as the more elaborate form. It is more graceful in ap- 
pearance, but one objection to it is that the mirror cannot be 
rotated above the stage for the illumination of opaque objects. 
The stand was extensively advertised about ten years ago, and 
was received with approval, and imitated in England, but during 
recent years it has not been heard from, at least in this its native 
country. It might be advantageous to some dealer, or to Mr. 
George Wale himself, if the “ New Working Microscope” could 
be revived. 
THE ARM. 
At the present day there is practically but one microscope arm 
in use by all the manufacturers. It of course differs in form 
with the various models as made by the various dealers, and it 
is of iron or brass, but so far as its connection with the body- 
tube is concerned, there is now really but one universal plan of 
accomplishing’ that object. This is the method devised by 
George Jackson, and called after his name, the Jackson model. 
In it the body-tube is, for the greater part of its length, sup- 
ported by the elongated surface of the arm through the interme- 
dium of the rack and pinion. This insures great steadiness of 
the body, both when the rack and pinion are in action, and 
when the microscope is subjected to the vibrations which are 
