16 THE AMERICAN MONTHLY [Jan 
camera; or a friction gear, in which a wheel shod with 
india-rubber is arranged to engage with the microscope 
milled head ; ora cord carried over the microscope milled 
head and over pulley wheels on either side of the base 
board having weights at the two ends, practically another 
form of friction movement. In practice the endless band 
has been the favorite, but it has possessed one drawback 
—it cannot be readily detached from the microscope. 
This difficulty was overcome by the cord with weighted 
ends. A very neat and simple fitting has been contrived 
by Mr. E. B. Stringer, which overcomes the obstacle with 
the endless band. The usual milled head of the camera 
rod, around which the cord is passed, is mounted on a 
frame the lower portion of which fits into a sleeve, per- 
mitting of the rod on which the milled head is carried 
being tilted forward when the band is to encircle the fine 
adjustment milled head, or to be removed; the band is 
then made taut by setting the fitting vertical again, a 
clamping screw being provided for securing it. In this 
position the long camera rod connects with it and actuates 
it. 
It may be mentioned that two or more milled heads of 
different sizes will often be found useful on the camera 
rod, for they will permit of the rate of movement being 
increased or diminished as may be desired. 
A NEw Susstace CONDENSER.—Several writers have 
advocated the use of a good low-power Substage Achro- 
matic Condenser, but nothing that really filled the gap 
was obtainable until the introduction of Mr. C. Baker’s | 
pew condenser. Zeiss’s Achromatic Condenser was right 
so far as it went, but it had several disadvantages. It 
was large—too large—and restricted the movements of 
the mechanical stages, also it yielded an aplanatic aper- 
ture of less than °70, yet the fact of its having a power of 
34-inch caused it to be appreciated, and largely used. 
Messrs. Watson & Sons have just introduced a new con- 
