Influence of Temperature on Vegetation - Vegetation varies with the Lati- tude and Height above the Sea Geographical Distribution of Land Plants Distribution of Marine Plants Corallines, Shell-fish, Reptiles, Insects, Birds, and Quadrupeds — Varieties of Mankind, yet identity of Terrestrial Heat Radiation - Transmission - Melloni's experiments - tion Pendulum Transmission through Crystals Dynamic Theory of Heat- - Mechanical equivalent of Heat Heat is the Force of Expansion - Steam - Work performed by Heat- Conservation of Force- - Mechanical Power in the Tides Dynamical Electrics and Non-electrics - Induction of the Electric Force Distribution Laws of Distribution- Heat of -The Voltaic Battery — Intensity- Quantity-Static Electricity, and Electricity in Motion- - Luminous Effects - Mr. Grove Discovery of Electro-magnetism - Deflection of the Magnetic Needle by a Electro-Dynamics - Reciprocal Action of Electric Currents - Identity of Electro-Dynamic Cylinders and Magnets - Differences between the Action of Voltaic Electricity and Electricity of Tension - Effects of a Voltaic Current Ampère's Theory — Dr. Faraday's Experiment of Electrifying Magneto-Electricity-Volta-Electric Induction - Magneto-Electric Induc- Identity in the Action of Electricity and Magnetism -- Descrip- Electricity produced by Rotation Direction of the Currents - Electricity from the Rotation of a Magnet - M. Arago's Experiment explained Rotation of a Plate of Iron between the Poles of a Magnet - Relation of Magnetism a Dual Power - Antithetic Character of Paramagnetism and Diamagnetism The Earth Paramagnetic - Properties of Paramagnetic Bodies - Polarity Induction Lines of Magnetic Force Currents of Electricity induced by them Proved to be Closed Curves - Analogy and Identity of Electricity and Magnetism - Terrestrial Magnetism Mean Values of the Three Magnetic Elements -Their Variations in Double Progression proved to consist of Two Superposed Variations Discovery of the Periodicity of the Magnetic Storms The Decennial Period of the Magnetic Elements the same with that of the Solar Spots Magnetism of the Atmosphere- Diamagnetism Magnetism on Paramagnetic, Diamagnetic Bodies, and on Copper, very different — Proof of Diamagnetic Polarity and Induction -Magne- crystallic Action - Effects of Compression, Heat, and Cleavage on Mag- netic Bodies Mutual Dependence of Light, Heat, Electricity, &c. &c. The Conservation of Force and the Permanency of Matter Primary Laws of Nature Definition of Gravity not according to that Law · Gravity only the Residual Force of a Universal Power - Magnetism of Ethereal Medium - Comets - Do not disturb the Solar System — Their Orbits and Disturbances M. Faye's Comet probably the same with Periods of other three known- Acceleration in the mean Motions of Encke's and Biela's Comets - The Shock of a Comet Dis- turbing Action of the Earth and Planets on Encke's and Biela's Comets Velocity of Comets - The Comet of 1264-The great Comet of 1343- Physical Constitution- Shine by borrowed Light Estima- The Fixed Stars- Their Number - The Milky Way - Double Stars Binary Systems-Their Orbits and Periodic Times - Colours of the Stars -Stars that have vanished - Variable Stars Variation in Sun's Light Parallax and Distances of the Fixed Stars - Masses of the Stars Comparative Light of the Stars - Proper Motions of the Stars Apparent Motions of the Stars-Motion and Velocity of the Sun and Solar System The Nebula - Their Number - Catalogue of them Consist of Two Classes - Diffuse Nebulæ Definitely formed Nebula - Globular Clusters - Splendour of Milky Way - Distribution of the Nebulæ - The Magellanic Clouds - Nebulæ round Diffusion of Matter through Space - Gravitation - Its Velocity-Sim- plicity of its Laws - Gravitation independent of the Magnitude and Distances of the Bodies Not impeded by the intervention of any Substance Its Intensity invariable-General Laws - Recapitulation THE CONNECTION OF THE PHYSICAL SCIENCES. INTRODUCTION. SCIENCE, regarded as the pursuit of truth, must ever afford occupation of consummate interest, and subject of elevated meditation. The contemplation of the works of creation elevates the mind to the admiration of whatever is great and noble; accomplishing the object of all study, which, in the eloquent language of Sir James Mackintosh, "is to inspire the love of truth, of wisdom, of beauty-especially of goodness, the highest beautyand of that supreme and eternal Mind, which contains all truth and wisdom, all beauty and goodness. By the love or delightful contemplation and pursuit of these transcendent aims, for their own sake only, the mind of man is raised from low and perishable objects, and prepared for those high destinies which are appointed for all those who are capable of them.” Astronomy affords the most extensive example of the connection of the physical sciences. In it are combined the sciences of number and quantity, of rest and motion. In it we perceive the operation of a force which is mixed up with everything that exists in the heavens or on earth; which pervades every atom, rules the motions of animate and inanimate beings, and is as sensible in the descent of a rain-drop as in the falls of Niagara ; in the weight of the air, as in the periods of the moon, Gravitation not only binds satellites to their planet, and planets to the sun, but it connects sun with sun throughout the wide extent of creation, and is the cause of the disturbances, as well as of the order of nature; since every tremor it excites in any one planet B is immediately transmitted to the farthest limits of the system, in oscillations which correspond in their periods with the cause producing them, like sympathetic notes in music, or vibrations from the deep tones of an organ. The heavens afford the most sublime subject of study which can be derived from science. The magnitude and splendour of the objects, the inconceivable rapidity with which they move, and the enormous distances between them, impress the mind with some notion of the energy that maintains them in their motions, with a durability to which we can see no limit. Equally conspicuous is the goodness of the great First Cause, in having endowed man with faculties, by which he can not only appreciate the magnificence of His works, but trace, with precision, the operation of His laws, use the globe he inhabits as a base wherewith to measure the magnitude and distance of the sun and planets, and make the diameter (Note 1) of the earth's orbit the first step of a scale by which he may ascend to the starry firmament. Such pursuits, while they ennoble the mind, at the same time inculcate humility, by showing that there is a barrier which no energy, mental or physical, can ever enable us to pass that, however profoundly we may penetrate the depths of space, there still remain innumerable systems, compared with which, those apparently so vast must dwindle into insignificance, or even become invisible; and that not only man, but the globe he inhabits-nay, the whole system of which it forms so small a part —might be annihilated, and its extinction be unperceived in the immensity of creation. A complete acquaintance with physical astronomy can be attained by those only who are well versed in the higher branches of mathematical and mechanical science (N. 2), and they alone can appreciate the extreme beauty of the results, and of the means by which these results are obtained. It is nevertheless true, that a sufficient skill in analysis (N. 3) to follow the general outline to see the mutual dependence of the different parts of the system, and to comprehend by what means the most extraordinary conclusions have been arrived at,-is within the reach of many who shrink from the task, appalled by difficulties, not more formidable than those incident to the study of the elements of every branch of knowledge. There is a wide distinction between the degree of mathematical acquirement necessary for |
