5i8 Sir ceorge shuckburgh’s Obfervations 
Determination of the Bafe . 
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Ch. Ft. In. Temper. 
Length of the bafe ab (fee the Chart) by the chain, \ 
fifttime, - - — 1 55 10 o 
Ditto, fecond time, — — — 55 9 9J 
The mean, — - — 55 9 10-87 
Pt. In. 
By frequent previous obfervations I determined C 4 ) the length 
of the chain by comparifon with the brafs ftandard rod | 50 O o 
reduced to 6o° of heat, — — ^ 
Correction for 13!° of heat from expanfion, — +0 o 05 
Diameter of the pins or arrows, one of which was ufed at -j 
each chain, and in fuch manner, that this correction be- r + 0 o 16 
came always -j- — — — 
Correct length of the chain as it was ufed in meafuring the 1 
bafe, ° _ _ - - I 5 ° 0 21 
Multiply by the number of entire chains in the bafe, — 55 
2750 11 55 
Add the parts of a chain, — — + 9 10 87 
True length of the bafe, as it was meafured, — 2760 10 42 
Correction for the defeCt of level, taken with an inftru- 1 _ Q 
ment made on purpofe, each time the chain was placed, J 
The true horizontal diftance between a anda becomes, 2760 9 66 
Deter- 
(d) It may ‘be required, to what precifion I could determine the length of 
•my chain? I think certainly to within of an inch, or of the whole 
length. The common Gunter’s chain of the fhops is always fubjeCt to fpring 
and ftretch confiderably; mine was made of hardened fteel, on purpofe to avoid 
this defeCt. It however ftill preferved fome degree of elafticity, for when 
pulled with a force of about ten pounds, it feemed =0,12 inch longer than 
iwhen laid gently on the floor without being flretched at all : the affumed length 
vf the chain was fuch as feemed to me probable from a moderate tenfion in 
^common 
