Meafurement of a Baje c?i MounlloW- Heath. ^i^^"^^ 



■ \t will be remembered, that in carrying on the operation 

 with the deal rods, double pickets were left in the ground at 

 the twenty-feventh ftation, anlwering to the extremity of the 

 Sioth rod fi-om the firff, or the 560th from the laft end oi" 

 the bafe. Now, on arrival at this point, the 560th glafs rod 

 overfliot the filk thread, ftretched from one picket to the other, 

 2.525 inches. Here again we find, that the lengthening * of 

 the deal rods from the moifliure of the atmolphere differs but 

 little from what it has been eftimated at by comparifon with 

 the ftandard, being over- rated only two-tenths of an inch on 

 the 560 rods. In this day's operation, in paffing the bridge laid 

 over the old river, the meafurement, inftead of being made in 

 the hypothenufal, w'as carried on in the level line, for the 

 ;lpace of twenty rods, namely, fifteen rods of the twenty- 

 feventh, and five of the twenty-fixth hypothenufe ; which 

 occalions the alteration in the reduction of thefe two fpaces, 

 ITiarked with afteriiks in the general table. 



As fome trouble had been found to attend the eroding of 

 ■the great road, in the firft meafurement, owing to the num- 

 ber of carriages that were continually pafiing, the depth of 



In. 



* 560 deai;.( -f 1.39^0 for i° excefs of heat of the brafs fcale from 62" 



50.0 aeaa; r 

 rods'Zr J 

 1 1 209 ft. I 



to 6:5 



+ 5.258 eftimated expanfion from moifturcj 



+ 6^648 equation of the 560 deal rods 



\ c +^-343 for 6" excefs of heat of the brafs fcale from 62° io 68''. 

 j^,^° ?1^ \ + 1.821 obferved expanfion-^f glafs \ from columns . I nh 



— 1. 1 91 obferved contraftion of ditto J and 12th. 



— 2.525 over-fli,Qt the fil)c-thread. 



+ 6.448 equation of the 560 glafs rods. 



i'ods =: 

 i 1 200 ft. 



..f-rr?rt- 



f Difference .over-rated irt the exnaufipn of the 560 



O o o 2 the 



