of an Arc of the Meridian. 427 
and one of cast iron, both of ten feet in length, is found to be 
o 5 ooooi part of an inch; therefore, the length of the chains, in 
the temperature of 54 0 , agreeing with the points on the bar, 
will be A = 100 feet -f 0,1325 inches. 
B == 100 feet -f 0,0778 inches. 
In the Phil. Trans, for 1795, page 437, their lengths, in the 
same temperature, as deduced by Mr. Ramsden, are stated to 
be A = 100 feet -f- 0,11425 inches. 
B — 100 feet -j- 0,05825 inches; which gives a dif- 
ference something less than -A- of inch between their present 
and former lengths. 
In the reduction of the preceding base, I have supposed the 
working chain A to be 0,12363 parts of an inch too long before 
the measurement began. If to this the whole wear be added, 
viz. 0,00384, we shall have the length of it, 100 feet -f 0,1275 
parts of an inch ; which differs only Tq 5 — from the late deter- 
mination of Mr. Berge. 
Calculation of the Sides of a Series of Triangles , extending from 
Dunnose , in the Isle of Wight , to Clifton , in Yorkshire. Plate 
XV. 
In the former accounts of the trigonometrical operations it 
will be found, that triangles have been carried on from Dunnose 
to Arbury Hill. It will be proper to give them in this place, 
that the series may be complete, thereby superceding the ne- 
cessity of frequently referring to those papers. 
