[ 36 4 ] 
dilatations of quickftlver, p. 695. Elaftic force of moift air fuperior to that of dry, 
p.705. 712 — 714. Concerning the elaftick force of air, p.748, 749. 755, 754. An 
experiment to determine hydroftatically the fpecific gravities of air and quickfilver, 
with a given temperature and prefibre, and remarks thereon, p. 557 — 570. Expe- 
riments on the expanfion of air in the manometer, p.689—696. Thermometricai 
fpaces compared with thofe of the manometer, p. 697. Experiments for determining 
thea&ual expanfion of common air in the manometer affedcd by the heat of 212°, 
P . 698—7:5. 
Air-pump , an account of fome experiments made with one, on Mr. Smeaton’s principle ; 
together with fome experiments with a common air-pump, p.614. Defcription of 
Mr. Smeaton’s pear-g2ge, p.614 — 616. Air in the pump expanded 4000 times* 
p.617. Enquiry from whence this .great fuperiority of expanfion could pro- 
ceed, p. 617. Difagreement between the pear-gage and the other gages, p. 6i8 # 
622. Difagreemet accounted for, p. 622—644. Experiment in which the apparatus 
was made as free from moilfure as pofiible, p. 624. Near agreement between the 
pear-gage and the barometer, p. 625. To difcover whether a vapour from moifture 
might not be contained in the fubftances ufed, p. 625 — 627. Elaftic vapours arofe 
from the leather and box-wood ufed, and influenced the bc.rometcr-gages, p. 627. 
Pear-gage not affedted by the vapour, ibid. Experiments on leather, allum, oil, and 
tallow, to find from which the vapour chiefly arofe, p. 628. Arofe principally from 
the leather, ibid. To determine that the moifture in the leather gave the vapour, 
p. 629, 650. The eifedl of vapour arifing from fmall quantities of fluids, and from 
fome fubftances, p.630, 631. Wet leather, ufed to connedl the receiver and plate, 
prevents the pump from exhaufting to any confiderable degree, p. 652. Different 
degrees of heat atfedl exhauftion, p. 633. Comparative excellency between the pump 
on Mr. Smeaton’s principle, and a common one, p. 633, 634. The effedl of water 
ufed in the barrels of pumps to make the piftons move air tight in them, p. 634, 
635. Remarks concerning Mr. Smeaton’s pump not exhaufting to as great a de- 
gree as the pump here ufed, p. 635 — 637. Further experiments made with the fame 
air-pump, the refult of which were different from the former, p. 637 — 646. Degree 
of cold produced by the evaporation of aether under a receiver whilft exhaufting, 
646—648. 
Alps. An account of Mont Saleve, p. 515, w. 527. An account of the Mole, 
p. 533 — 539. Barometrical obfervations to afeertain the heights of the Alps, 
P* 5 1 3 > 
Alte Segen , a mine in the Hartz, its height determined by barometrical obfervations, 
p. 421, 422. 441—443. 
Altitudes determined by the barometer, 515— 53 2 * 53 ° — 54 ^* 549 ? 55 0, 55 2 — 554 * 
592 — 597. Rule for meafuring fuch heights, p/683. 687. 734, 735. 757, 758. 
762, 763, k. The rule which anfvvers in middle latitudes will not in the frigid and 
torrid 
