Heat, 193. Radiation and conduction of, 205. One of the chief agents in chemistry, 310. Our ignorance of the nature of, 310. Abuse of the sense of the term, 311. The general heads under which it is studied, 312. Its most obvious sources, 312. Animal heat, to what process referable, 313. Radiation and conduction of, 314. Solar heat differs from terrestrial fires, or hot bodies, 315. Principal effects of, 317. The antagonist to mutual attraction, 322. Latent heat, 322. Specific heat, 323. Herschel, sir William, his analysis of a solar beam, 314. Hipparchus, his catalogue of stars, 276. Holland drained of water by windmills, 61. Hooke almost the rival of Newton, 116. Huel Towan, steam-engine at, 59. Huyghens, his doctrine of light, 207. Ascertains the laws of double refraction, 254. Hydrostatics, first step towards a knowledge of, made by Archimedes, 231. Law of the equal pressure of liquids, 232. General applicability of, 232. Hypothesis, not to be deterred from framing them, 196. Conditions on which they should be framed, 197. Illustrated by the laws of gravitation, 198. Use and abuse of, 204. Induction, different ways of carrying it on, 102. Steps by which it is arrived at on a legitimate and extensive scale, 118. First stage of, 144. Verification of, 164. Instanced in astronomy, 166. Must be followed into all its consequences, and applied to all those cases which seem even remotely to bear upon the subject of enquiry, 173. Nature of the inductions by which quantitative laws are arrived at, 176. Necessity of induction embracing a series of cases which absolutely include the whole scale of variation of which the quantities in question admit, 177. Induced electricity, 333. Inertia, 223. Iodine, discovery of, 50. Efficacy of, in curing goître, 51. Isomorphism, law of, 170. Kepler, effect of his discoveries on the Aristotelian philosophy, 113. Nature of his laws of the planetary system, 178. Proofs of the Newtonian system, 179. Knowledge, physical facts illustrative of the utility of, 45. Diffusion of, how to take advantage of in the investigation of nature, 138. Lagrange, his improvements on Newton’s theory of sound, 247. His astronomical researches, 275. Lamp, safety, 55. Laplace, his explanation of the residual velocity of sound and confirmation of the general law of the developement of heat by compression, 172. His astronomical research, 275. His experiments on the dilatation of bodies by heat, 319. His study of specific heat, 323. Latent heat, 323. Laws, inductive, 171. General, 198. How applicable, 199. Illustrated by the planetary system, 201. Empirical laws, 178.