Index. 303 



Loadstone, account of the, i. 21 the, or natural magnet, 

 ib. comparative power of the, 23 properties of com- 

 municated to iron, ib. See also Magnetism. 



Longitude of heavenly bodies, what, i. 268 method of 

 ascertaining at sea, 338. 342. 



Looking-glasses. See Mirrors. 



Lunar caustic, how formed, ii. 247- 



Lunar tables, invention and use of the, 5. 341. 



Lutes, different sorts of chemical, ii. 123. 



M. 



Machines, the six simple described, i. 232. 



Magic lantern, principle of the, explained, i. 15Q. 



Magnesia, chemical account of, considered as one of the 

 earths, ii. iQl to 1Q5. 



Magnet, effects of the, i. 11 nature of the, 21 pro- 

 perty of the, 22 experiments on the power of the, 22, 

 23 the artificial, 23, 24. 



Magnetic attraction, i. 21 discoveries of Mr. Barlow 

 concerning, 33 needle, declination of the, 27 to 2Q 

 magnetic sand, a, 22. 



Magnetism, phenomena of, i. 11 lecture on, 21 ac- 

 count of the loadstone, ib. degree of a magnet's force 

 at different distances, 22 general power of loadstones, 

 23 method of making magnets, and different kinds of 

 them, 23, 24 poles of the magnet explained, 24 its 

 principle of repulsion, 25 the mariner's compass, and 

 its great use, 26 different means by which iron may 

 acquire the magnetic virtues, 30 entertaining experi- 

 ments in magnetism, 30. 34 theory of, imperfectly 

 developed, 32. 



Magnets, subject to the attraction of the earth, i. 29. 



Magnifying and diminishing properties of glass, i. 3. 



Marls, different kinds of them, ii. I7f>. 



Mars, particulars concerning this planet, i. 306. See also 

 2QO to 2g5. 304, 305. 



Matter, three forms under which it appears, ii. 57. 



Mean and solar time, difference between, ii. 5. 



Mechanic powers, lecture on, i. 233 the six different 

 kinds of these ; the lever, 233 : the wheel and axle, 

 238: the pulley, 239: the inclined plane, 241: 

 the wedge, 243 : the screw, 244. See also Motion. 



