76 THE MICROSCOPE. 
the under side of the cover-glass. “A” is not intended to be used 
with a cover, nor are the copies to be used uncovered. 
I append in a note below the table of measurements by Mr. 
Fasoldt, in order that your readers may have the means of judging 
whether my criticisms are just. The reader is also referred to the 
investigations of these various scales hitherto published in the pro- 
ceedings of the American Society of Microscopists, which should be 
accessible to every person who owns a microscope. 
Curcaco, 1889. 
MEASUREMENTS BY CHAS. FASOLDT, SR. 
Table showing the variation in measurements due to the different applica- 
tions of light and iiluminations. 
The image of 4; inch was the object on which these measurements were 
made, and was ruled on a glass disc of No. 2 covering glass, 000 inch in 
thickness. 
All measurements were taken on one and the same ruling, with the same 
microscope, objective and eye-piece, under the same focus, and having the 
microscope in the same position continually, and only changing the mirror and 
excluding the one light while the other was used. 
UNMOUNTED. 
LINES DOWNWARD. LAMP LIGHT. LINES UPWARD. 
Concave Mirror, . . +4; in. ~532;;— Concave Mirror, . . to in. zottoot 
Plane e - . poi. zo@ooc+ Plane i to in. ohtoot 
I]l. througn objective, 4, in. y5;55+ Ill. through objebiive! vo in. got hoot 
MOUNTED ON GLASS. 
LAMP LIGHT. DAY LIGHT. 
Concave Mirror,. . io in. 0 Concave Mirror, . . 4 in. 753955+ 
‘ ‘ 44 0 
Plane ; é 16 in. zotpoo t+ Plane : - « fo IM. zoFoao+ 
lll. through bijective 4 io In. zo8t4oot 
A number of comparisons were made at each position and in the same 
temperature. 
A Spencer objective was used for these measurements. But Bausch & 
Lomb and Gundlach objectives were also tried, obtaining the same results. 
The microscope used is one constructed on my late patents, and has a 
micrometer for measuring similar to a cob-web micrometer. But instead of 
cob-webs, three movable steel pointers are used, which are worked as fine as this 
metal will permit. The stage is mechanical, and the main slide is moved with 
great precision by a fine screw 100 threads per inch. 
THE KING MICROTOME.—NUMBERS 1 AND 2. 
J. D. KING. 
HIS microtome claims no superiority over other first-class 
instruments for ordinary histological work in animal tissues, 
but it is designed especially for hard service in botanical work or for 
