253 AN ACCOUNT OF THE 
When therefore the zero line of 4°5 considered with the first division of | 
3°4, the length of the pair was 599-949, and if the division corresponding te _ 
600 inches or fifty feet be required, we have 1-°000—051+-4—796 division. 
The comparator being at 1203. 
34. ‘ "THE preceding operations were all performed previously to the com- 
mencement of the measurement. ‘There was also.a comparison made with 
the chain, at the same time, but for a clearer view of the subject it will be 
better here to go on, and give an account of other determinations of the 
length of the rods made during: the measurement of the base from the brass 
scale. There were in all 8—in 3 of which the four rods were placed 
together, and the stepping made at once for all 4. In the other 9, only 
the pair 3.4 and 4.5 was measured, but we ean easily from those determina- 
tions deduce the length of all four, by means of comparisons made between 
the two pairs. These it will be proper to notice first. 
_ 35. Tue pair 3.4—4.5 had a similar ivory scale, as that of 1.2—-2.3 
that is to say divided into quarter inches, and each of those into tenths. 
During the measurement however it broke, and got loose, and it became 
necessary to apply another. The first point is then to determine the cor- 
respondence of the two scales, which may be done from the following 
double readings. 
Old Seale, New Scale, 
od 
720 315 
740 330 
798 Ti SEO 
“570 "240 
