4,2(5 An Account of the Measurement 
to sense, in our conclusions, if we consider Misterton Carr as 
situated on the mean surface of the spheroid. I shall, therefore, 
take 2634,2,7 feet for the true length of the base; and I think it 
cannot exceed or fail short of that quantity, more than two 
inches. 
Recent Comparisons of the standard and working Chains , with 
the points inserted l in the cast Iron Bar. 
In the reduction of the foregoing base, I have taken it for 
granted, that the standard chain is precisely of the same length 
as when it first came out of the hands of Mr. Ramsden. Cir- 
cumstances which need not be mentioned in this part of my 
paper, but which, in their proper places, will be explained, have 
induced me to get both the long chains remeasured. Mr. Berge, 
therefore, at my request, prepared the bar and plank, and lately 
went through the required operation. The particulars were as 
follow. 
The chain B was first measured in five successive removes, 
the first space of 20 feet having a thermometer in the middle of 
the bar, which stood at 4,8°; the second space or remove, having 
the same thermometer at 48°, 2 ; the third, at 48°, 5 ; the fourth, 
at 48°, 8 ; and the 3th, at 48^8 ; which gave the total length of 
the chain =.100 feet -j- 0,077 parts of an inch, in the mean 
temperature of 48°, 6. 
The standard A was then measured in five successive re- 
moves ; the thermometer at each remove being 48°, 5 ■ — 48 °, 6 — 
48°, 7 — 48°, 8 — 48°, 8 ; which gave the length of A = 100 feet 
-j- 0,132 parts of an inch, in the temperature 48,' *7. 
From the Table of expansions in Vol. LXXV. of the Phil. 
Trans, the difference between the expansion of a rod of steel 
