[ +95 ] 
telefcope defcribed, ibid. Boning rods, and their ufe, defcribed, p.412. Cup and 
tripod for preferving the point upon the ground, where the meafurement was difcon- 
tinued at night, and refumed next morning, p.412. Difference between meafuring 
with a rod of twenty feet, and with rods of twenty feet three inches, p. 412. Brafs 
cup ufed on thefe occafions defcribed, p. 413. 415. Nature of the tripod (tab. 
XVIII.) explained, p.413. Method ot lufpending the plummet from any part of 
the deal rods indifferently, p.414. Wheels for terminating, in a permanent manner, 
the extremities of the bafe, tab. XVIII. ibid. Mr. Mylne’s improved machines for 
certainly referring to the fame point on any occafion of correcting or repeating the 
work (reprefented in tab. XVIII.), p.415. Rough meafurement of the bafe with 
the chain, and determination of the relative heights of the ftations by means of the 
telefcopic fpirit level (tab. XVI. and XVII.), p. 416. The firft meafurement of the 
iouth-eaft fedtion of the bafe completed in three hours and a half, p. 417, 418.. 
The fame fedtion re-meafured, wi h the probable caufe of the variation, p. 418. 
The operation with the chain fulpended, and why, p. 419. Defcription of a hold- 
faff for the rear-end of the chain, invented by Col. Pringle (reprefented by two ele- 
vations adjoining in tab. XVII.), ibid. The operations refumed by meafuring twice 
With the chain forwards and back again the fecond fedtion of the' bafe, ibid. The 
level of the firft and fecond fedtion of the bafe taken, with an account of the fpirit- 
Jevel made ufe of, p. 420. The firft general table relating to the levels of the 
bafe explained, ibid. p. 421. Col. Calderwood’s method of computing the difference 
between the hypothenufal diftances of 600 feet each, and the reduced bafe diftances,. 
p. 420. Tracing of the bafe with the tranfit inftrument, p. 421, 422. Confequence of 
delaying the ufe of that inftrument, p.422. Levels of the third fedtion taken, and 
the rough meafurement thereof with the chain completed, p. 422, 423. Reful t of the 
examination of the length of the chain in different temperatures, p. 423. Defcent 
from the lower end of the bafe to the furface of the Thames at Hampton, p. 42 
Meafurement of the bafe with the deal rods, p. 425. Method of performing that 
(operation, p. 426. Difference of meafuring by coincidences and contadls accounted 
lor, p. 427, The two firft hypothenufes re-meafured^ with the refuit, p. 428. 
Their Majefties prevented by the weather from feeing the nature of the operations, 
p. 429. Method of difeovering the error of the chain at each ftation, p. 429. In- 
conveniences occurring from the humid and dry ftate of the atmofphere, &ct. p. 430. 
See Expanfibility. Different companions of the rods with the ftandard, and the 
jefult, p. 432, 433. Near agreement between the refuit by the deal rods, and that 
furnilhed by the rough meafurement with the chain, accounted for, p. 433.. Mea- 
furement with the deal rods finiihed, ibid. Expnnfion of the deal rods, p„ 
434 * 43 ^* See Riga Red-wood, Deal Rods. Mr. Ramfden’s obfervations of 
the different expanfions, p. 435, Operations on Hounfiow-Heath totally Im- 
pended, p. 438. Companion made in the beginning of September at Spring 
Grove, when the rods were in their dry or contracted Hate, and the remeafure- 
ment 
