8o Captain Kater on the comparison of 
contrary sense, the higher number indicating defect, and vice 
versa. 
Readings. 
Thermometers. 
1 st interval. 
2 9>5 
54o°') 
2 d. 
10,0 
53,5 J-Ramsden's bai 
3 d - 
10,0 
53 >5 J 
4 th. 
1^5 
— 
5 th. 
10,0 
53,0 Forty inch bar 
6 th. 
1 9>° 
Mean 
15.9 
The difference of temperature of the two bars being so 
small, may safely be neglected. 
The micrometer microscope was now set to 15,9 divisions, 
and the apparatus being laid on the 40 inch bar, the inter- 
section of the wires of the left hand microscope was brought 
to the middle of the line on the gold pins, and the piece of 
latin brass was moved along the bar, till the middle of the 
line drawn upon it appeared in the intersection of the wires 
of the micrometer microscope. The whole having been 
carefully examined, the micrometer microscopes were with- 
drawn. 
_ The tracing microscope was next brought over the 40 
inch bar, and placed so that the intersection of its wires ap- 
peared upon the middle of the line traced upon the brass ; the 
brass was then slid away, and a line drawn with the cutting 
point upon the gold surface. 
I had next to compare the distance thus obtained, with the 
mean of the six intervals on Mr. Ramsden's bar. 
