[ 49 « ] 
me'nt of the fame fpace the next morning, when, being left out on purpofe, they 
had contra&ed all the humidity they could, p, 439, 440. Defcription of the 
glafs rods, ultimately ufed to determine the length of the bafe, tab. XIX. p. 441 — 
449. The cafe containing the tube de'cribed, p.441. Manner in which the middle 
of the tube is made fall to the middle of the cafe, p. 442. Fixed and moveable ends 
of the tube oefcribed, p. 443. Fixed and moveable apparatus defcribed, p. 444 — 447* 
Mahogany lid on the top of the cafe defcribed, p. 447. Method of afcertaining the 
length of the glafs rods, p. 448. Difpofition of the Hands for the double meafurement 
with the chain and glafs rods ; defcription of the apparatus then applied to the ends of the 
chain ; and ultimate continuation of the meafurement with the glafs rods alone, tab. 
XVII. and XIX. p. 449. Reafons for reje&ing the deal rods, ibid. Commencement 
of the operation for the double meaiurement, p. 4^0. 4^3. Apparatus attached to the 
firft end of the chain, p. 451. Ditto for the lait end (to the right-hand fide of tab. 
XVII.) , p. 452. Companion of the contraction of Heel and glafs, with the error of the 
chain in defeft, p. 454. Farther experiments with the chain given up, and why, p.455. 
His Majefty honours the operation with his prefence, p. 456. Equation of the deal rods 
and of the glafs rods, on 3100 feet, ibid. Difference over-rated in the expanfion of the 
1560 deal rods, p. 457» Meafurement with the glafs rods completed, p. 458. Equa- 
tion of the 1370 deal rods and of the 1370 glafs rods, with the difference over-rated ia 
the total expanfion of the deal rods, p. 459. Conjedure concerning the caufe of the 
eftimated and real expanfion of the deal rods, ibid. p. 460. Defcnption of the mi» 
crofeopic pyrometer, ufed for determining by experiment the expanfion of the metals 
concerned in the meafurement of the bafe, tab. XX. p. 461 — 472. The microfcopic 
pyrometer (tab. XX.) defcribed, p. 462—- 472. Ufe and defcription of the fixed 
mierofcope, p. 466. Ditto of the micrometer, p. 467. Ufe of two eye glaffes ia 
snicrofcope., p, 468. Scale of the pyrometer explained, p. 469. Account of the 
experiments with the pyrometer, p. 472—476. Ultimate determination of the bafe 
on Hounfiow-ileath, p. 476—478. General table of the bafe, fhewing the relative 
heights of the cations above the fouth-eaft extremity near Hampton Poor-houfe, the 
reduction of the hypothenufes, and the correction for the temperature of the glafs 
rods, whereby the true length is obtained in the heat of 62 degrees, p. 479. Table 
of the expanfion of metals, deduced from experiments made with the microfcopic 
pyrometer in 1785, p. 480. 
BlaJh, Mr. See Specific Gravities. 
Jinuguer. See Specific Gravities. 
Breedon, Leicefierfhire, obiervations on the lime-mountain there, p. 4, 
Brook , Mr. bee Vacuum. 
Bruce, Robert, M. D. See Averrboa CaramboJa. 
Burning Mountains. See Mo me Garou , Carihbee IJlands * 
C. Calderwoofi 
