﻿ACROSS THE ?EXIXSULA OF INDIA. S^lV 



The coffers were tlien put upon the pickets, and 

 having all tlietr bottoms of the same tliickness, they 

 therefore formed the plane in wliich the chain was 

 to be extended. 



When any hypothenuse was terminated, a line, 

 with a pkimmet, Mas let fall from the arrow upon 

 the feather edge of the chain ; and the point on the 

 ground was marked, wliich was defined by the 

 point of the plummet, (for a brass register head was 

 there unnecessary,) and the height of that extremity 

 of the chain, from the ground, was carefully taken. 

 The new-hypothenuse, therefore, commenced from 

 that same point, and the arrow at the beginning of 

 the next chain was made to coincide with a plumb 

 line falling to the said point. And the height also 

 of that end of the chain, from the ground, was 

 taken ; by which means, the ascent or descent of 

 the conmiencement of the new hypothenuse wa.s 

 determined. 



When the chain was extended in the coffers, it 

 was fixed at one end to the drawing post, and from 

 the other an 8§ inch shell was suspended. The lead- 

 ing register head was then brought by the finger 

 screw, so that some division might correspond with 

 the arrow. Five thermometers were then put into 

 the coffers, (one into each,) and there remained for 

 some minutes, a cloth at the same time covering 

 them. They were then taken out, and the mean 

 temperature marked down. This was done to every 

 chain, and a mean of each hypothenuse was after- 

 wards taken, and the result served to determine the 

 equation arising from expansion and contraction, 

 for correcting the whole apparent length of the 

 base. 



Every thing having been prepared, the measure- 

 ment commenced on the 14th October, and was 

 completed on the 10th December: the particulars 

 thereof will appear in the following table. 



y 4 Ob^ 



