264 J. J. Woodward on Photographing 
time may ily be given with a piece of velvet, or a card- 
board screen held in the hand. For shorter exposures some 
mechanical contrivance is indispensable. That alluded to above | 
seems to answer every purpose, and is arranged as follows: A ) 
wooden screen is fixed between the microscope and the sensitive | 
plate, as close as convenient to the microscope. To prevent | 
side lights reaching the plate, the screen is connected with the 
window shutter by velvet curtains, which can be turned aside 
to manipulate the instrument, and be let down at the prope’ = | 
time. circular hole, three inches in diameter, is made in the 
screen opposite the tube of the microscope for the transmissioR | 
of the image. In front of this a light yee slides loosely UP 
and down, held in place by a cleat of wood on each side, 1 
design being to permit the x area to fall edge foremost with 8 =} 
little friction as possible. The shutter may be made of thit 
metal, of wood, or even of card-board. i 
: Vv of slit, from a fraction of an inch 
ten inches, can be ein ae art of the shutter below _ = 
rture through which the im e passes when 
fixed in place before the Sst is made. 02 
