TRANSACTIONS OF SCIENTIFIC SECTION. 73 
plications. The method by which these circular saws 
can be made to cut in true planes, is applicable as well to 
the large saws which would be needed for the sawing of 
marble slabs as to the smaller ones used in cutting litho- 
logical sections. 
JANUARY 24, 1888—SIXTIETH REGULAR MEETING. 
Charles N. Arnold, presiding. 
A letter from Dr. A. T. Woodward, of Brandon, Vt., 
concerning the ‘‘ Frozen Well,’’ was read and discussed 
informally by the members. 
Dr. C. B. Warring also presented a brief paper upon 
“Moonlight and Electric Light,’ as follows: 
MOONLIGHT AND ELECTRIC LIGHT. 
A few days ago, on Tuesday evening, November 29th, 
the air was very clear and a little cold, the thermometer 
standing at 30°. The moon was sensibly full, and at a 
rough guess 30° above the horizon. It occurred to me 
that it was a good time to make an approximate com- 
parison of the electric light with that of the moon. The 
former was the arc light, and was rated at 1,200 candle- 
power. The burning carbons were protected by a large 
elobe of clear (¢. é., unground) glass. The lamp is about 
22 feet above the ground. 
The first comparison measurement was made at 7 
o’ clock, by the method of shadows. I carefully paceda 
distance from the lamp till the shadows of a lead pencil 
made by the moon and the lamp falling side by side on 
white paper were of equal intensity. To get this point 
more accurately, I moved toward the lamp till the lamp 
- shadow was decidedly the darker, and then did the same 
for the shadow made by the moon, and after each moving 
went back to point of equality. The results came out 
with surprising agreement. The result of all was that 
the point of equality was 60 paces from the foot of the 
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