153 
By this arrangement a very great degree of accuracy in 
reading is obtainable. Thus in the present instrument the 
quadrant is set 5 inches distant from the hinge, and when 
set at 0 - 5 inches on the quadrant it gives a rise of 1 in 10 ; 
consequently the ether in the U tube has to move 10 inches 
for 1 inch of vertical rise. The rule for getting the result 
may be stated thus : — 
Divide the space between the hinge and the quadrant by 
the quadrant elevation, now divide the movement of the 
ether by the quotient, and the product is the true vertical 
movement nearly. 
Thus, suppose, as before, the quadrant elevation to be 
05 inch, the distance from hinge to quadrant 5- 0 inches, 
and the ether’s movement 1 inch : then 
J5_ 
0-5 
TO 
= 10 and — - = 0T 
10 
inch. 
Or again, the quadrant elevation being 0*2 inch, the other 
quantities the same : then 
5 TO 
A O = 0*25 and — = 0'04 inch. 
0-2 1-25 
These results, though not absolutely correct, will in most 
cases be sufficiently so ; but where rigid accuracy must be 
had, the following table will supply the means : — 
Quadrant 
Elevation in 
Quadrant 
Elevation in 
10 inches. 
Hypotenuse. 
10 inches. 
Hypotenuse. 
'1 inch ... 
... 10*00049 
IT inch ... 
... 10-06035 
•2 „ ... 
... 10-00199 
1-2 „ ... 
... 10-07174 
•3 „ ... 
... 10-00449 
1-3 „ ... 
... 10-08414 
■i „ ... 
... 10-00799 
1-4 „ ... 
... 10-09752 
•5 „ ... 
... 10-01248 
1-5 „ ... 
... 10-11187 
•6 „ ... 
... 10-01799 
1-6 „ .... 
... 10-12714 
•7 „ ... 
... 10-02447 
1-7 „ ... 
... 10-14347 
•8 „ 
... 10-03199 
1-8 .... 
... 10-16061 
•9 „ ... 
... 10-04049 
1-9 „ ... 
... 10-17888 
1-0 „ ... 
... 10-04987 
2-0 „ ... 
... 10-19803 
hirst find what aliquot part of 10 the quadrant elevation 
was ; find this in the quadrant column. Opposite this will 
