450 Mcijor-GencralV^OY's Account of the 
and that by the glafs rods adhered to, as every way deferving 
of the preference ; bee a ufe of the obvious impropriety there 
would be, in taking a mean between one kidifputably good 
and another lefs perfect, however fmall or trifling in reality 
the difference of the two might ultimately be found, on a 
minute and ferupuious companion. 
In order, therefore, to avoid any repetition of the operation 
with the glafs rods, and at the fame time to give fomething 
like a fair trial to the chain, it was propofed, that a double 
meafurement fhould be carried on with both at once ; that is 
to fay, that the number of Hands, 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 fuccefiion on the fame Hands. Accordingly, the various 
articles having; been fent to the north-wefl end of the bafe on 
the evening of the 17th of AuguH, the operation of the dou- 
ble meafurement commenced next morning the 18th. 
By referring to tab. XVII. it will be fee n, that feventeen 
Hands were neceflary for .fupporting the chain, the apparatus 
attached to each end of it, and. ten coffers, whereof every five 
made about ninety-eight feet, in order that one length of the 
chain being meafured off in the firff five, it might be drawn- 
forward into the laff five, and fo on. Thefe feventeen Hands 
were difpofed of in three groups of three each, and four inter- 
mediate, between the central and extreme groups. The mid-? 
die or Hide Hand of each group (fo diflinguifhed becaufe fome 
of them had brafs Hides 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 Hands, inter- 
mediate to thofe in the center of each group that fupported 
c the 
