380 
CAPTAIN KATER ON THE ERROR IN 
so constructed would be liable from curvature, could not exceed one ten- 
thousandth of an inch. 
The support of the scale which I have caused to be made for the Government 
of Russia, and the comparisons of which, with the Imperial standard yard, are 
given in the present paper, is a brass bar one inch and three-quarters wide, and 
half an inch thick. The plate carrying the divisions is one-tenth of an inch 
thick ; but were I to construct another, it should not exceed half this thickness. 
This plate is made to slide freely upon the surface of the bar in a dovetailed 
groove, and is fixed to the bar at its middle point by a single screw in the 
manner before described. The divisions are thirty-six inches, marked by dots 
upon the surfaces of gold pins let into the brass plate. An additional inch 
beyond zero is divided in like manner into tenths of an inch. This description 
will serve also for that of the scale before alluded to, made for the Government 
of Hanover. 
The following experiments were made with the Russian scale, the arrange- 
ments being the same as before detailed. 
Russian scale with wires .04 of an inch diameter. 
From 0 to 36 inches. 
Without Wires. 
A Wire under 
the middle. 
Wires under 
the ends. 
Error when curved 
upwards. 
Error when curved 
downwards. 
Sum of 
Errors. 
div. 
div. 
div. 
div. 
div. 
div. 
69 
66 
75 
71 
66 
73.5 
71 
65 
74 
70 
67.5 
75 
70 
63.5 
75 
70 
64 
73.5 
Mean 70.5 
65.3 
74.3 
7-3 
1.7 
9-0 
2.1 Reduction to the Chord. 
72.6 
I now employed wires of .05 of an inch in diameter, and these supported the 
bar wholly above the surface of the marble. 
