212 THE NORTHERN MICROSCOPIST. 
slides of various widths, from 1 inch to 23 inches, it is strongly 
made, well finished, and of excellent workmanship throughout, 
besides which loose springs are supplied, fitting into corresponding 
holes in the turntable, convenient for making rings in any other 
position than that of the true centre of the slide. 
This instrument is shown in fig. 40, the letters being explained 
as follows :— 
A.—Ordinary wood block with steel pivot, on which the brass 
table revolves. B,—Two brass springs which fit into holes in the 
table, and may be used when the slide is required to be out of 
centre; when not in use they fit into holes in the wood, as shown 
above. D.—Revolving table, with milled wheel below for rotation. 
H.—Brass annulus or ring which revolves concentrically on the 
table D: on the ring H are screwed two conically headed pins J J, 
332 Of an inch apart exact, to allow the 3x1 slip to be placed 
diagonally between them. F F.—Two similar pins in plate D, so 
placed, that upon revolving the ring H they, in conjunction with 
the pins J J, firmly grasp the opposite corners of the glass slip, and 
cause the centre to coincide with the centre of the tablep. 1.— 
Brass pin for more easily revolving the ring H, for securing and 
liberating the glass slip, which is done by moving the ring H in the 
opposite direction. 
Parkes’ MicroscopE LAMP wITH CooLING EVAPORATOR.— 
This Lamp, independently of its patent cooling arrangement, will be 
found to fulfil all the conditions of most lamps hitherto con- 
structed for microscopic use; with the addition of an effective 
shade and reflector. With the shade may be used the patent 
evaporator as shown in fig. 42, which prevents the radiation of 
heat upon the observer’s head, and, by the gentle and imper- 
ceptible evaporation of the water contained therein, the surrounding 
air is moistened, and thus rendered less irritating to the eyes and 
respiratory organs. 
These facts may be readily demonstrated by placing a thermo- 
meter, say eight inches from the lamp, when it is first lighted. 
This: should be on a level with the top of the shade, which is the 
usual position of an observer’s head when using the microscope. 
It will be found that after the lamp has been burning an hour, 
the thermometer will only indicate a rise of three or four 
degrees, whereas, with most lamps having a terra cotta or metallic 
shade, the temperature would be raised from twelve to fifteen 
degrees. 
C is a bronzed copper cylindrical shade, 3} inches diameter, 
with hood at front to prevent the upward reflection of light. At 
the back is a parabolic reflector, which will slide out for cleaning, 
and, when desirable, a disc of cardboard may be placed over this 
reflector, for ‘ white cloud” illumination, At the front is a tinted 
