C 487 ] 
f 
A N 
I N D E X 
IT O THE 
SEVENTY- THIRD VOLUME 
OF THE 
PHILOSOPHICAL TRANSACTIONS. 
A. 
r zjG R UME> that term explained, p. 195. 
Air. See Eudiometer , Refifiance of Air. 
Air-pump, defcription of an improved one, and the account of fome experiments made 
with it, by Mr. Tiberius Cavallo, p.435. Almoft every part of the air-pump im- 
proved by Mr. Smeaton, ibid. The principal imperfedion of the belt air-pumps 
never removed till the invention of that here deferibed, p. 436. Defcription of it, 
p. 437—444. The working of this pump explained, p. 444 — 447. Experiments 
made with it, p. 447 — 432. 
Algol (the bright ftar in the head of Medufa), a feries of obfervations on, and a difeo- 
very of, the period of the variation of the light of that ftar, in a letter from John 
Goodiicke, Efq. p. 474. All hitherto known concerning the variation ot this ftar is 
comprifed in a paflage of Du Hamel’s “ Hiftoria Regia: Scientiarum Academia:,” 
ibid. Obfervations exhibiting a regular and periodical variation in that ftar, 
47^—482. Agreement between the author’s obfervations and Mr. Edward Pigott’s, 
p. 473. 480. 482. The ufual and greateft brightnefs of Algol, p.473. Obferva- 
tions on Algol ; its brightnefs and magnitude, p. 476. Duration of its variation, p. 
480. And the regular period of its occurring rendered confpicuous by a table, 
P Vol. LXXIII. s f r Mrrpifi, 
S f f 
