Aid to Teachers and Students in Natural Philosophy: Being the "key" to Dr. Johnson's Philosophical Charts : Accompanied with Facsimiles of the Charts on a Reduced Scale

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A. Ranney, 1856 - Physics - 60 pages

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Page 36 - When a ray of light passes from one medium to another, it is refracted so that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities in the two media.
Page 26 - To explain the construction of the common barometer, and to shew that the mercury is sustained in it by the pressure of the air on the surface of the mercury in the basin.
Page 33 - Light diminishes in intensity, and hence in its power to illuminate objects which it strikes, as it recedes from its source. The intensity of light diminishes as the square of the distance from its source increases. Calling the quantity of light falling upon a visiting card at a distance of 2 feet from a lamp flame 1, the quantity falling upon the same card at a distance of 4 feet is J, at a distance of 6 feet it is ^, and so on. This is the meaning of the law of inverse squares, as applied...
Page 3 - KT/HBBB, each being 34 by 53 inches, are well bound, and strongly mounted on cloth and rollers. They are printed with white lines on black ground, and most of the drawings are colored, making them distinctly visible from any part of the largest school-room; preventing them from becoming soiled, besides giving them a neat, lively, and ornamental appearance. From the late City Supt. of Schools of Brooklyn, KY Dr. Johnson's " Philosophical Charts" have been prepared especially for the uo of Schools...
Page 2 - These Charts embrace, besides several original illustrations, all the essential diagrams and drawings contained in the popular and commonly used text-books upon this branch of education ; numbering about three hundred drawings, illustrating clearly the principles of Natural Philosophy, as generally taught in schools. They are accompanied by a Key, giving in brief the essential explanation.
Page 6 - ... art only when musical notes were invented, by which it became possible to express harmonies of sound to the eye. The symbolism in both cases is perfectly arbitrary ; nevertheless, when once acquired, it becomes an instrument of wonderful intellectual power. But if the mind is capable of being thus greatly aided by ocular signs, when there is no natural relation between them and the objects they represent, how much more must its power be multiplied when the symbols it employs assume the pictorial...

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