180 Sir George Shuckburgh Evelyn’s Endeavours 
(§. 51.) Lest, however, it should be suspected, that Mr. 
Troughton’s scale, with which I have made these comparisons, 
is not sufficiently correct for this apparent preference, I will 
now give the result of my examination of that scale, from one 
end to the other. I set the microscopes to an interval of nearly 
6 inches, correctly speaking, it was 6,00013 inches, taken from 
a mean of the whole scale ; and, comparing this interval suc- 
cessively, I found as follows. 
Inches. Inches. Inches. 
viz. from o to 6 - = 6,00025* 
6 to 12 - = 6,00013 
12 to 18 - = 6,00020 
18 to 24 - = 6,00000 
24 to 30 - _ = 6,00007 
30 to 36 - = 6,00033 
36 to 42 - = 5,99980 
42 to 48 - = 6,00020 
48 to 54 - = 6,00010 
54 to 60 - = 6,00023 
Mean of all - - = 6,00013. 
From whence it appears, that the greatest probable error, 
without a palpable mistake, in Mr. Troughton’s divisions, 
is = ,00033 i nc h ’ against which, the chance is 9 to 1 ; and 
* It is not pretended, that in this and the foregoing observations, the quantity of any 
interval can be determined to the precision of the one hundred thousandth part of an 
inch ; but it is presumed, that with the assistance of the microscopes, the ten thou- 
sandth part of an inch becomes visible ; and, as a mean is taken from 3 or 4 times 
reading off the micrometer at each trial, it has been deemed not unreasonable to set 
down the quantities to five places of decimals. 
Error, or difference 
from the mean. 
-|- ,00012 
,00000 
- . i '■ ■■ •• . . ' - 1 
- + ,00007 
— ,00013 
- — ,00006 
-j- ,00020 
■ — 500033 
+ ,00007 
■ — ,00003 
,00010 
