[ 3 
F- 549? 550. Correfponding obfervation at Geneva, tending to prove the faid defeft, 
p. 551, 552. Other experiments on Mont Saleve, p. 352. Comparifon of the fir ft 
feries, 553. Comparifon of the fecond feries, ibid. Comparifon cf the third 
feries, p. 554. Comparifon of the fourth feries, ibid. All proving the exiftence ■ f 
the defedl in Mr. de Luc’s rules, p. 554, 535. Quantity of the defcd, from the refult 
of all the barometrical experiments, p. 555, 536. An experiment to determine 
hydroftatically the fpecific gravities of air and quickfilver, with a given tempeiature 
and prefTure, p. 357 — 561. Statical and barometrical experiments nearly 
agree, p.561. A fmall difference in the equation for the expanfion of air and 
quickfilver, by a change of temperature, from what Mr. De Luc’s obfervations have 
given it, p. 56 2 — 569. Remarks on the foregoing inquiry, p. c6 9, 570. Precepts 
and tables for calculating any acceHible heights or depths from barometrical obfer- 
vations, p. 571 — 597. 
Mountains of Thibet, mulk-deer common there, p. 485, 486. 
Madge, Mr. John, his dire&ions for making the belt compolition for the metals of re- 
flecting telefcopes; together with a defcription of the procefs for grinding, polilhing, 
and giving the great fpeculum the true parobolic curve, p. 296. See Telefcopes . 
Musk-deer , common in the mountains of Thibet, p. 485, 486. 
Mutton , the Thibetians Angular method of preparing it, p. 473. 
N. 
Nairne, Captain, his remarks on the parts of mails of fliips covered with lamp-black and 
tar, or lamp-black and oil, efcaping injury by lightning, p. 85, 86. 
Nairne, Mr. Edward, his account of fome experiments made with an air-pump on Mr. 
Smeaton’s principle; together with fome experiments with a common air-pump 
p. 614. See Air-pusnp . 
Newton, Sir Ifaac , the flrft propofer of polilhing the metal for refle&ing telefcopes with 
pitch, p. 344. Pitch fuppofed to be the only fubftance in nature, that is perfeCllv* 
calculated for that purpofe, p. 345 — 347. 
North American B if on, the fame as the great bufraloe in the wilds of Africa, p. 40. 
O. 
ObjtEl-glafs micrometer, an error in its ufe, p.799 — >801. Method of corredling the' 
error, p. 801 — 812. 
Ohfervatory . An account of the Bramins obfervatory at Benares, p. 598. See Brand ns 
obfervatory . 
Oder Brucke , in the Hartz, its height above Claufthal determined by barometrical obfer- 
vations, p. 429. 444 — 449. 
Oil and lamp-black, or lamp-black and tar, preferve the parts of malls of ihips covered, 
with it from injury by lightning, p. 85, 86. A curious inllance of this kind, 
5 S 2 p. 86— 
