332 THE MICROSCOPE. 
which, in the older stands, will be found on the lower end of the 
body, at the front; on some of the oldest models and a few of 
the newest, it will be attached to the stage, but in the most recent 
it is placed at the back of the arm. The mechanism through 
which it works, is almost as varied as the names of the makers, 
levers, screws, rollers and springs being used singly or in com- 
bination. 
Those stands whose fine adjustment is on the nose-piece, or 
lower end, of the body are objectionable because, unless the 
workmanship is super-excellent, the parts: will sooner or later 
work loose, and every time they are touched the body will wab- 
ble and the image will dance. And the fine adjustment screw is 
touched very often. During an observation, the microscopist 
moves the stage with one hand, and keeps the fingers of the 
other on the fine adjustment screw continuously, constantly 
altering the focus slightly, so as to judge of the structure of the 
object by the changes in the appearance of the different optical 
sections practically cut by the objective. 
When applied to the stage, a part of the een is tilted every 
time the screw is turned, so that the surface must necessarily be 
more or less oblique, and the object and the slide must be tilted 
out of the horizontal position, thus changing the parallelism 
between the front of the objective and the surface of the ohject, 
or of the cover glass. Another important point which has been 
urged against this method is, that when the sub-stage condenser 
is used it is thrown out of focus every time the stage is tilted, 
because the position of the object is changed by being raised or 
lowered, and in delicate investigations, where this piece of sub- 
stage apparatus is exceedingly valuable, its focus must be steadi- 
ly maintained. Other microscopists contend that while the 
device is incorrect in theory, it is not objectionable in practice. 
Mr Edward Pennock, an accomplished microscopist with the 
firm of Messrs J. W. Queen «& Co., says in reference to this form 
of fine adjustment, which is used on one of their “Acme” stands: 
“An objection is sometimes made that one side of the stage plate 
is moved while the other is not, thus elevating one side more 
than the other. We only ask those to whom this may appear 
an objection, to make a practical and careful test. They will 
find that this objection is invalid in practice as the range of 
motion required is very slight.” The motion, however, is still 
