The London encyclopaedia, or Universal dictionary of science, art, literature, and practical mechanics, comprisiong a popular view of the present state of knowledge . each other, therewill still be only two images, but the ray ordi-narily refracted in the first will become extraor-dinary in the second, and the extraordinary,ordinary. But at all intermediate positions ofthe two crystals there will be a subdivision ofeach ray, consequently four images: these fourimages will be of equal intensity when theprincipal sections of the two crystals are at anangle of 45° to each other; at all other angl
The London encyclopaedia, or Universal dictionary of science, art, literature, and practical mechanics, comprisiong a popular view of the present state of knowledge . each other, therewill still be only two images, but the ray ordi-narily refracted in the first will become extraor-dinary in the second, and the extraordinary,ordinary. But at all intermediate positions ofthe two crystals there will be a subdivision ofeach ray, consequently four images: these fourimages will be of equal intensity when theprincipal sections of the two crystals are at anangle of 45° to each other; at all other anglesone or other of the images diminish in intensity,as the principal sections approach to a perpen-dicular or parallelism ; not by the coalescenceof the two images, but by the gradual diminu-tion of the intensity of one, and the augmenta-tion of that of the other. In plate III. figs. 1,2, and 3, we have supposed the rhomboids re-duced to the form of cubes in all three, the axisis denoted by .r .r, and the direction of the raysby the lines passing through the figure, and theletters e and o the extraordinary and ordinary ^S fio. 7. Fi( Fu/.4.
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Keywords: ., boo, bookcentury1800, bookdecade1830, bookpublisherlondontteggson
