134 Gen. Roy’s Account of 
As a proof that the expanfion of the chain was accurately 
determined, I (hall clofe this fe&ion with a remark repeatedly 
made by the two gentlemen entrufted with the execution of 
this laft meafurement. At the clofe of each day’s work, the 
two fcales marking the extremities of the laft chain (after re- 
giftering the divifions of co-incidence) were left upon their 
refpe&ive pofts until the next morning. They were fecured 
during the night, from being difturbed by cattle, with a cer- 
tain number of the fpare pofts driven into the ground around 
them. A tent was alfo pitched between the two, where fome 
men of the party conftantly lay, by way of a guard for the 
whole apparatus. On the recommencement of the operation 
the fubfequent morning, the chain being applied anew to the 
brafs fcales \ if the temperature continued the fame, the co- in- 
cidences were found to be equally accurate as on the preceding 
night ; but if it had changed one or two degrees, the chain 
never failed unequivocally to fhew it, by falling fhort of the 
divifions on the fcales, if the cold had increafed, or by over- 
reaching them if it had diminifhed. 
Finally, with refpedt to the fubje£t of thefe bafes, it is here 
to be remarked, that the bafe of verification in Romney Marfli 
makes with the meridian of the pipe at High Nook an angle 
of 54 0 28 56" | north- weftward; and that bn Hounflow 
Heath makes with the meridian of the pipe at Hampton Poor- 
houfe an angle of 44 0 41 ! 49", alfo north -weftward* 
General 
