A New Calculating Machine. Bij Edward M. Nelson. 3 
divisions on A C or B C were one inch apart those on CD would have 
to be 1 * 4142 inches apart. 
To solve — = - — T , whilst taking out (a) on A C as before take 
x a b ° w 
(b) out on D 0, instead of on B 0, and read the answer on B C. 
Let 
then if 
but if 
Examples. 
a — 2*1, and b = 6 ' 5; 
-=-+b a = 1-59; 
x a b 
1 _ 1 
x a 
1 
b 9 
x = 3-10. 
By having the diagonal line graduated much trouble and incon- 
venience is thereby saved. 
I am sure the thanks of all optical workers are due to Mr. 
Tamblyn-Watts for such a simple labour-saving machine. 
