After perusing the account of Dr. Richardson's experiments, the mind reverts to the formation of natural fossils, and the remarkable imitation of nature with pressure and heat, which produces these quasi-fossil moulds in plaster of Paris. Fossils have been spoken of as "the medals of creation;" who would dare (unless they were makers of artificial flint-head arrows) to imitate so closely? But the forgery in this case is an advance in science, and no doubt will assist the geologist and paleontologist to make speculations (this time) founded on actual experiment. In bringing this work to a conclusion, the writer desires it to be understood that he has endeavoured to fulfil a promise made in his first elementary work on science, and that was, to try to lead the youthful and unlearned reader further on in the pursuit of that science; the beginning of which, Sir Humphrey Davy said, is pleasure; its progress knowledge; its objects truth and utility. It is said that Demosthenes first conceived his passion for eloquence upon hearing the orator Callistratus, and witnessing the applauses with which his performance was rewarded; that Tycho Brahé resolved to devote his life to astronomy in consequence of his witnessing, when a child, an eclipse of the sun. Surely amongst the thousands of young people who attend scientific lectures, there must be undeveloped geniuses who might, if they read and practise scientific experiments, become as useful and as celebrated as a DAVY, a FARADAY, or a WHEATSTONE! LIGHT-continued. Simms's spectrum apparatus, 93 Solar spectrum, to obtain the; apparatus for Sources of light, 5, 8-14 Spectacles, 66, 67, 68 Spectroscope, the, 23, 94, 95, 96, 102 Specula, figuring and mounting; the alt-azi- Specula, to silver glass; to prepare, clean, Specula, on working glass, 46, 47, 48 Stokes, Professor, 92, 93, 97 T. Table of the indices of refraction, 52 Tait, Professor P. G., 2 Talbot, Mr. Fox, 94 Telescope, the compound, 56 Telescopes, silvered glass reflecting, 41-48 Test candles used in photometry, 15, 16, 17 Thaumatrope, the, 74 Thermo-electric pile, the, 3, 4 Thompson's reflecting galvanometer needle, 3 Tobin, Thomas, 27, 28, 29, 30 Tourmaline, the, 116, 117, 118, 119, 121 Transversal vibrations of light, 112, 122 S. Selerite slides, 119 Shadow Blondin, the, 12, 13, 14 Silvered chain and electric light, 7 Silvered cord vibrating, 7 Silvered glass reflecting telescopes, 41-48 W. Waves neutralized by the superposition and Absorptive power of bodies, 198, 199 Alcohol or minimum thermometer, directions Amount of expansion in solids, liquids, and Anomaly of contraction of stretched or ex- Anomaly of expansion and contraction in HEAT-continued. Capacity for molecular motion, 151 Cast iron frame broken by contraction, 130 Celsius, 136, 137 Centigrade scale, the, 136, 137 Centrifugal theory of elasticity, 178 Changes of the state of aggregation, 162, 163 Chemical action, 152, 153 Coefficient of expansion of gases, the, 143 Combined steam, 193 Combined vapour engine, 193 Common effects of heat, 127, 128 Conduction, 147-160 Conductivity of gases, 156, 159 Conductivity of liquids, 157, 159 Conductors of heat, good and bad, 148, 149, 153, 156, 157, 158, 159 Conservation of energy, 152 Conversion of light rays into heat rays by Conversion of potential into actual energy, Conversion of the expansion of gases into power or motion, 144 Conversion of water into vapour, 168, 169, 170 Cornish boiler, the, 192, 193 Crystallization, 134 Cylinder valve and condenser, 186 |