4' CO Major-General Roy's jIc count of the 



and that by the glafs rods adhered to, ns every way defervlng- 

 of the preference ; becaufe of the obvious impropriety there 

 would be, in taking a mean between one indifputably good 

 and another lefs perfeft, however fmall or trifling in reality 

 the difference of the two might ultimately be found, on a 

 minute and fcrupulous comparifon. 



Ill order, therefore, to avoid any repetition of the operatioa 

 with the glafs rods, and at the fame time to give fomethlng 

 like a fair trial to the chain, it was propofed, that a double 

 ineafurement fhould be carried on with both at once ; that is 

 to fay, that the number of ftands, and feveral other parts of 

 the apparatus, fhould be fo far augmented, as to admit the 

 chain to be placed twice in advance, and then the rods to fol- 

 low in fucceffion on the fame ftands. Accordingly, the various- 

 articles having been fent to the north-weft end of the bafe on. 

 ,the evening of the 1 7th of Auguft, the operation of the dou* 

 ble meafurement commenced next morning the iSth. 



By referring to tab. XVII. it will be feen, that feventeen-. 

 ilands were neceffary for fupporting the chain, the apparatus- 

 attached to each end of it, and ten coffers, whereof tVQry five 

 made about ninety-eight feet, in oi-der that one length of the 

 chain being meafured off in the firft five, it might be drawn 

 jjfqrward into the laft five, and fo on. Theie feventeen ftands - 

 were difpofed of in three groups of three each, and four inter- 

 mediate, between the central and extreme groups. The mid-- 

 die or Aide ftand of each group (fo diftinguiflied becaufe fome 

 of them had brafs flides on their tops) fupported the handle of" 

 the chain, and of courfe received the traces made at the feather- - 

 edged pieces of brafs, terminating the beginning and ending of 

 the hundred feet. Thus, there were in all fix ftands, inter-- 

 mediate to thofe iu the center of each group that fupported 

 5 ' the 



