THE MICROSCOPE. 269 
constantly shaking a city house, or even the most secluded 
work table. 
Many years ago what is called the “ Ross Model” was used by 
Ross, of London, as his method of supporting the body-tube, 
although he did not originate it, and has now abandoned it for 
the Jackson method. In it the arm was produced horizontally, 
the extremity of this prolongation having inserted into it the 
lower end of the body-tube, all the rest of the body extending 
upward entirely without support. The rack, instead of being 
attached to the body and moved by a pinion within the arm, 
was cut in the side of the arm itself below the horizontal projec- 
tion which bore the body-tube. The eye piece was at the long 
end of a lever, so that every vibration of the tube was transferred 
to its upper free end, and there greatly increased in effect; con- 
sequently, unless the workmanship was perfection, the image 
danced about in a most aggravating way. In Ross’s stands, 
however, as made by himself, the workmanship was so super- 
excellent that but little dancing of the image occurred, unless 
the surroundings were exceedingly unfavorable. As the method 
is now universally abandoned, it has historic interest only. 
The elongated surface in the Jackson model upon which the 
body bears by means of the rack, has been taken advantage of 
by the manufacturers to increase still further the steadiness of 
that part. Bulloch in his first-class stands cuts two V-shaped 
grooves the entire length of the part, into which fit and smoothly 
slide two V-shaped tongues attached to the body-tube, while the 
latter also bears a central projecting rib with two lateral flanges, 
all of which fit into corresponding grooves and depressions. 
Zentmayer’s stands have a somewhat similar though less vom- 
plex arrangement of projecting pieces and flanges, with the 
admirable addition of a spring so arranged as to bear contin- 
ually upon the parts, and not only aid in the steadiness of the 
whole, but compensate for any loss by wear and tear. Other 
makers have adopted modifications of these plans whicn belong 
to all mechanics in common, and can be claimed as the device 
of no special one. 
In the most desirable of our modern stands the arm carries 
the fine adjustment screw on its back, as well as the pinion of 
the coarse adjustment on the front, while in the majority it also 
bears the mirror bar and often the sub-stage apparatus, besides 
