58 PHOTO-MICROGRAPHS. 
of the tube for admission of light coincides with 
the optical axis of the microscope. 
The proper position of the heliostat-shelf is ascer- 
tained by adjusting the instrument in accordance 
with the printed directions accompanying it, and 
then placing it at such an elevation that, when it is 
in the same meridional plane with the microscope, 
the light from the mirror falls in the tube con- 
taining the eight-inch lens (in the Woodward 
governor), and is well centred upon the achromatic 
condenser of the microscope. 
The operating-room need not be more than five 
or six feet wide by ten or twelve deep. The pho- 
tographic manipulations may also be conducted 
in this room, but it is more convenient to have 
another small room, or closet, for this purpose. 
If there be a second window in the operating- 
room, this must also be carefully closed, to exclude 
actinic light; but sufficient non-actinic light may 
be admitted through one or two panes to enable 
the operator conveniently to find his way about 
the room, This is accomplished by substituting 
ruby glass for the common window-glass; or more 
economically, by fastening two thicknesses of good 
buff envelope-paper over the panes. 
The admirable work of Surgeon Woodward, with 
which most microscopists are familiar, was done at 
the Army Medical Museum, Washington, D. C., in 
a room arranged as above described. Dr. Wood- 
ward has his ground-glass screen supported upon 
a small but substantial table, which moves upon 
rollers, and can be readily placed wherever desired. 
