Biot's investigations of meteors--The observations of Brandes and Benzenberg on the velocity of falling stars--Professor Olmstead's observations on the meteoric shower of 1833--Confirmation of Chladni's hypothesis of 1794--The aurora borealis--Franklin's suggestion that it is of electrical origin--Its close association with terrestrial magnetism--Evaporation, cloud-formation, and dew--Dalton's demonstration that water exists in the air as an independent gas--Hutton's theory of rain--Luke Howard's paper on clouds--Observations on dew, by Professor Wilson and Mr. Six--Dr. Wells's essay on dew--His observations on several appearances connected with dew--Isotherms and ocean currents--Humboldt and the-science of comparative climatology--His studies of ocean currents--Maury's theory that gravity is the cause of ocean currents--Dr. Croll on Climate and Time--Cyclones and anti-cyclones,--Dove's studies in climatology--Professor Ferrel's mathematical law of the deflection of winds--Tyndall's estimate of the amount of heat given off by the liberation of a pound of vapor--Meteorological observations and weather predictions. CHAPTER VI. MODERN THEORIES OF HEAT AND LIGHT Josiah Wedgwood and the clay pyrometer--Count Rumford and the vibratory theory of heat--His experiments with boring cannon to determine the nature of heat--Causing water to boil by the friction of the borer--His final determination that heat is a form of motion--Thomas Young and the wave theory of light--His paper on the theory of light and colors--His exposition of the colors of thin plates--Of the colors of thick plates, and of striated surfaces,--Arago and Fresnel champion the wave theory--opposition to the theory by Biot--The French Academy's tacit acceptance of the correctness of the theory by its admission of Fresnel as a member. CHAPTER VII. THE MODERN DEVELOPMENT OF ELECTRICITY AND MAGNETISM Galvani and the beginning of modern electricity--The construction of the voltaic pile--Nicholson's and Carlisle's discovery that the galvanic current decomposes water--Decomposition of various substances by Sir Humphry Davy--His construction of an arc-light--The deflection of the magnetic needle by electricity demonstrated by Oersted--Effect of this important discovery--Ampere creates the science of electro-dynamics--Joseph Henry's studies of electromagnets--Michael Faraday begins his studies of electromagnetic induction--His famous paper before the Royal Society, in 1831, in which he demonstrates electro-magnetic induction--His explanation of Arago's rotating disk--The search for a satisfactory method of storing electricity--Roentgen rays, or X-rays. CHAPTER VIII. THE CONSERVATION OF ENERGY