jj.r2 Mtijor-G eneral '^.oy''s Account cf the 



from the dart on the feather-edge coincides with the point df 

 commencement on the ground underneath ; for which purpofe 

 there is a hole in the top of the ftand through which the wire 

 palles. The apparatus iland, thus ferving to pull back the 

 chain, was commonly loaded with double weights, placed on 

 the two hindermofl: legs. ^ 



The apparatus for the laft end of the chain confifts, like tlie 

 ■former, of a fmall wooden frame that can be readily flipped 

 upon any of the common ftands, as may be iQ&n by referrinp* 

 to the right-hand lide of tab. XVII. This frame carries a 

 pulley, over which a rope pafl'es having fourteen pounds weight 

 fufpended at one end of it, while a forked iron hook at the 

 other end lays hold of the ftraight part of the brafs handle. By 

 means of thefe two apparatufes the chain is always kept to the 

 fame degree of tenfion in its coffers, in each of which a ther- 

 mometer was placed to indicate the temperature ; the whole 

 being covered up from the direft rays of the fun by a narrow 

 piece of linen cloth, ftretched along it from one end to the other. 



Each coffer confifted of three boards about half an inch 

 thick. The fides were about five inches deep, nailed at the 

 middle to an interfole bottom of four inches, in fuch manner 

 as to be reprefented in feftion by the letter H. They were ill 

 made, being by their parallelogram fliape apt to warp, which 

 might have been prevented by giving them the:figure of the 

 cafes of the glafs rods, that is to i^^y^ making thena wide in the \ 

 middle and narrow at each end. 



We are now to proceed to give fome account of the double 

 mealuremcnt with the chain and glafs rods ; wherein it muflbe 

 remembered, as alfo in continuing the operation with the glafs 

 rods alone, that in referring to the map for the daily progrefs 

 in the v/ork, .we are going from the forty-fixth towards the firft 



jdation ; 



