322 Nine Inch Conical Rain Gage. 
of the cone. Three inches fall of rain will then fill such a cone. Since 
the contents of similar cones are as the cube roots of their heights, 
in order to make a scale for measuring the rain fallen into such a cone, 
obtain the cube roots of 30 numbers, proceeding arithmetically from 
one, for the tenths of the three inches severally, and multiply each 
cube root by such a number as, being multiplied into- the cube root 
of 30, shall give 9. That number is found to be 2.9. This will 
give 4.18, for three tenths of an inch; If then the 30 cube roots be 
multiplied by such a number as, when multiplied into the cube root 
of 30, will give 4.18, they will give the divisions of the scale for hun- 
dredths of the three first tenths of an inch. This multiplier is found 
to be 1.345, very nearly. 
According to these rules the following table is constructed. 
LE Ii. fess Ns i] il. Ha; IV. 
a) i. 2.90 |. 1.345 16 | 2.521 | 7.30 | 3.39 
2 | 1.260 | 3.65 | 1.69 17 | 2.571 | 7.45 | 3.46 
3 | 1.442 | 4.18 | 1.94 18 | 2.621 | 7.60 | 3.53 
4 | 1.587 | 4.60 | 2.13 19 | 2.668 | 7.74 | 3.59 
5 | 1.710 | 4.96 | 2.30 20 | 2.714 | 7.87 | 3.65 
6 | 1.817 | 6.27 | 244 21 | 2.759! § 3.71 
€) 4913 | 5.55.) 257 22 | 2.802 | 8.12 | 3.77 
8 5.80 | 2.69 23 | 2.844 | 8.24 | 3.83 
9 | 2.080 | 6.03 | 2.80 24 | 2.885 | 8.36 | 3.88 
10 | 2.154 | 6.25 | 2.90 25 | 2.924 | 8.48 | 3.93 
IL | 2.224 | 6.45 |- 3. 26 | 2.962 | 8.59 | 3.98 
12 | 2.290 | 6.64 | 3.08 LEAS 8.70 | 4.03 
13 | 2.352 | 6.82 | 3.16 28 | 3.036 | 8.80 | 4.08 
15 | 2.467! 7.15 | 3.32 | 30! 3.107!9. | 4.18 
The first column contains the 30 numbers. The second, the cube 
roots of them. The third, their products multiplied by 2.9, for 
tenths of inches; and the fourth, their products multiplied by 1.345, 
for hundredths. 
To measure the fall of rain in such a hollow cone, fixed with its 
base uppermost and horizontal, put down to its apex a stick of wood 
sharpened at its lower end, and mark the water-line on it; then the 
distance from that to the point of the stick, applied to a scale thus 
graduated, will show at once, in inches and decimals, the quantity of 
rain fallen; or the distance may be applied to a common scale of in- 
ches and decimals, and by comparing the length thus found, with the 
numbers in the third and fourth columns of the table, the same re- 
sult will be shown. 
