t 68 4 ] 
miefiriciiy* Care of the St. Vitus’s dance by, p. i. Pulfe quickened, and an eruption 
like the itch produced in all the joints, by pofitive, p. 4. An amifpafmodic, p. 5* 
Fleftricity. Improvement of the apparatus, p. 454. Account of an anticonduflor, 
p. 454. Advantages of this apparatus, for exhibiting e> periments'more analogous 
to the natural effe&s of lightning from the clouds, than it is poffible to do w th 
only one conduttor pofitively electrified, p. 433. Experiments to (hew that the two 
conductors are differently Charged, as foon as the cylinder is put in motion by 
turning the wheel, p.456. Experiment to Ihew the poffi ility of compreffiug the 
eleCtric matter, tho’ the globes are perfectly infulated, p. 458. Experiments to Ihew 
the advantages of pointed over blunt conductors, p. 460. 
Ele&ricity. Account of an eleCtric'al plate machine, p. 663. Flat glaffes ufed to excite 
it, inflead of globes or cylinders, p. 66 1. Pafte-board imbibed with copal or amber 
vannfh fubftituted to the glafs difks, p.667. The machine defcribed, and inftances 
of ftrong electricity excited with ir, p. 669. Machines of this kind lofe their 
power by being kept in cold rooms, 671. How to preferve them, or redore their 
powers when loft, ibid. The conduCt >r of a paper machine muft not be furnifhed 
with metallic points, p. 672. Account of a plated machine, with a difk of baked 
wood, boiled in linfeed oil, p. 671. 
Equatorial . Apparatus applied to the equatorial inftrument for correcting the errors 
arifmg from the refraction in altitude, ^*.$32. Inconvenience of the method hitherto 
ufed, p. 333 1 Hfes of a fpirit level fixed to ilic c^uatuiial inftrurnent, p. 334. 
Equinoxes. On the preceffion of them produced by the fun’s attraction, p. 505’. Pre- 
cefficn different, according as the ring at the equator is confidered as fluid, *or 
as hard and compaCt, p. 506 — 509. Problem of the preceffion of the, requires no 
principles but the received doCtrine of motion, and the application of the lever, 
p. 509. Problem to determine how much any particle of the earth is affeCted by 
the unequal aCtion of the fun, p. 510. 
Fric Profperin , Mr. {hewed that the obfervations of four months on the comet of 1770 
could not be reprefented by a parabolic orbit, p„ 84. Conjectured from thence that 
Its orbit might be fenfibly ellipticals p. 84. 
F. 
Feld-fpar. Change of clay into, p. 22. The Labradore ftone one, p. 25. How diA 
tinguifhed from crvftal and quartz, p. 27. 
'Fontana , Abbe. Electrical plate machine contrived by, p. 663. 
Forfait, Mr. a memoir of his, to indicate the beft and cheapeft methods of freeing 
navigable canals from banks of fand and earth formed in their beds, which render 
them too fhallow ; recommended, and an account given of it, p. 598. 
Free 
