-4-3^ 'Major-General Roy*s Account of the t 



<quanhty of the melted metal on the irons, made ufc of for 

 xlrawing them at the glafs-houfe. 



The week of rainy weather, which ended the month of 

 •July, occafionlng, as has been faid, a total fufpenfion of the- 

 opeiations on the heath, was employed in procuring a fuffi- 

 cient number of glafs tubes (one whereof was not lefs than 

 twenty-fix feet long) and regulating with Mr. Ramsden 

 every thing concerning their conftrudion into meafuring rods. 

 The defcription of them we (hall however defer until the time 

 of their application in the field, after having finifhed the opera- 

 tion with thofe of deal. 



On Monday the 2d of Augufl, the operations on the heath 

 were refumed at 8 h. 30^ A.M. Ly comparing the rods with 

 the ftandard, which they were found to exceed by one-fortieth 

 of an inch, the temperature then being 66°. The forward 

 end of the rod now placed over the tripod at N' 27, com- 

 pleting the Sooth length, reckoned from the lower end of 

 the bafe by rods of 24:; inches each ; and theie being equal 

 to 810 rods of 240 inches; it was judged proper to mark a 

 p(^ii;i,tiiipon the ground correfponding to this forward end, that | 

 it might , be referred to in returning back with the mealurement 

 by the glafs rod§. - This was done by fuiking two fmall pickets 

 iiito the ground, about a foot afunder, one on each fide of the 

 bafe, and at right angles to it. A filk thread being then | 

 flretched over the tops of the pickets, and gently moved on 

 till it touched the filver .wire fufpended from the end of the | 

 rod, fine notches were then made with a pen-knife in the tops 

 of the pickets, whereby the thread could be replaced in the 

 iame fituation ; which being dope, the pic}cets were covered over 

 •with earth. In the courfe of this day nine hypothenufes were 

 measured ; and at 7 h. P.M. the tripod was placed at the thirty- 



fixth 



