to ascertain a Standard of Weight and Measure. ijg 
on Troughton’s; (thermometer at £i°,o;) viz. Mr. Bird’s 
measure was shortest ,0018 ; or, shortest on 3 6 inches = ,0012, 
And 12 inches, or 1st foot, on Mr. inches. 
Aubert’s 
2d foot, 
3d foot, 
4th foot, 
5th foot, 
Therefore the mean foot is 
on Mr. Trough- 
ton’s scale, from 
6 inches to 18 
inches ; the ther- 
mometer being at 
5o°,o. 
= 1 b9999 
= 12,0005 
11 >9996 > 
12,001 9 
12,000 6 
12,0005 
The greatest error in this scale appears to be about = ,001 2 
And the mean probable error - - = ,0006. 
(§. 50.) The Royal Society’s scale, compared, was as follows : 
58 inches on Mr. Bird’s were equal to 57,99912 inches on Mr. 
Troughton’s : (thermometer 50°,5) 
viz. Mr. Bird’s measure was shortest ,00088 
Or shorter on 36 inches - - ,00054 
32 inches on the same were equal to - 31,99967 
viz. Mr. Bird’s was shortest by - ,00033 
Or, on 3 6 inches, by - ,00037 
The mean of these two comparisons is ,00045 
And, by so much, is Mr. Bird’s scale shorter, in three feet, than 
Troughton’s. 
And 12 inches, or 1st foot, of the inches. " 
Royal Society’s scale, is - = 12,00013 
2d foot of ditto = 1 1,99957 
3d foot of ditto = 12,00027 y ton's scale ; 
4th foot of ditto = 11,99990 r 
5th foot of ditto = 12,00063 
6th foot of ditto = 11,99823 
7th foot of ditto = 12,00000 
The mean of these seven feet is = 11,99982 
And the greatest error in these divisions = ,0008 
And the mean probable error - = ,0004. 
A a 2 
on Trough- 
ton’s scale; 
the thermo- 
meter at 51 0 . 
