434 Major-General Roy*s Account of the 
chain, if the fur face had been one uniform inclined plane, 
throughout its- whole extent. But, although the afeent of 
Hounilow-H.eath Is fo. fmall, and fo gradual, as to occafion 
little more than half an inch of reduction, from the 46 hypo- 
thenufal- to- the 46 bafe diftances, into which it is. divided, as- 
may be feen by referring to the table ; yet each of thefe by- 
pothenufes containing again many other fmall irregularities, all 
of which affect the meafurementby the chain,, in. proportion too 
their number and height, in- every fpace of 600 feet, their; 
united effects, including the lateral, deviations from the true 
line in meafuring, do fomewhat more than compenfate for the. 
extra-length of the chain, as will be feen hereafter in com- 
paring the length of the bafe juft now obtained with that , 
given by the rods. 
The weather, which during the greater part of June had; 
been wet, became ftill worfe towards the end of the month 
and firft week of July;, fo much fo, that even if the deal rods, 
had been, ready they could, not have been ufed with advantage. 
The foldiers, neverthelefs,. were not idle,, being, when the” 
weather w r ould permit, partly employed , in clearing the Heathy, 
and partly in aftifting Mr. Reynolds in the furvey, towards? 
the perfecting of which many chief points were fixed by? 
means of my aftronomical quadrant,, placed for. that purpofe at? 
feveral different ftations of the bafe., At this time too (July- 
8th) I levelled from the lower end of the bafe to the furface off 
the Thames at Hampton, and found the defeent to be 36-11 
feet.. 
