INDEX.

19O n. Of the Minutes and Seconds in a Clock, !.197 n. Of the striking Part, i. 198 n. Of Wind-mills, i. 219-

Mediterranean, Vapours exhaled from, ii. 13m In-flux from the Ocean, whence, ii. 14 n.

Mediums, Resistance of, si 312, & seq.

Meniscus, why best in Catadioptric Microscopes, iii.50 n. Species of Lens, iii. 19.

Mer ca tor’s Projection, what, iii. 309. Of greatest Usein Sailing, ibid. sis seq.

Melody, and Harmony, composed of twelve Notes, ii,255.

Mercurial Pump, a curious one, invented by Mr. Ho-fiins , and improved by Dr. Defaguliers, ii. 57 n. is?seq. Peculiar Manner of working, ii. 58 n. Ra-tionale of, ibid. & seq. Its Structure plainly repre-sented, ii. 61 n.

Mercury in the Barometer indicates the Quantity of th$Air, ii. 125 n. 'A Table shewing its Ascent andDescent, ii. 139 n. Mean Altitude of, what, ii. 145,Weight of a cubic Inch of, ii. 150 n.

Meridian, what, iii. 174. General, what, ibid. Ho-rizon, what, iii. 174*

Meridional Parts, Table of, for the oblate Spheroid, byMr. Murdoch, iii. 3 1 3 n •

Metals, Dissolution of, accounted for, 1. 38 n.

Meteors formed from Vapours, i. 34 R -

Metonic Cycle, what, ii. 56.

Micrometer , what, and how constructed, >11. 52 n, ,New Pocket one, iii. 53 n. Theory of a new one,iii. 372. General Rationale of, 111. 372, & seq.Applied to the refracting or reflecting Telescope,iii. 377. Its Application to refracting .Telescopesless convenient, iii. 381. Liable to some Objec-tions, iii. 384.

Microscopes, single, Use of, iii. 12 . Several Sorts of,illustrated, iii. 42 n. & seq. Single, focal Dis-tances of determined, iii. 44 n. Double, what,iii. 45 n. Catadioptric, Construction of, iii. 49 n.Reflecting or catoptric, Construction of, iii. 50:,.sower of magnifying estimated, ibid. & seq. Pocket