This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...as from the plane mirror and is said to be totally reflected. The angle of incidence, when the angle of refraction is 90, is the critical angle. When the critical angle is passed the ray is totally reflected; such a reflecting surface is the best reflector known. The sparkle and glow of the diamond is largely due to the fact that its index of refraction is large, and therefore light soon passes the critical angle and is totally reflected. If white light be passed through a glass prism, as in Fig. 59, it is twice refracted in the same direction, and, besides its deviation from the original direction, it is found to be dispersed, that is, separated into different colors. These colors correspond to light of different wavelengths, much as pitch in sound depend upon different wave-lengths. The red, which is least refracted, is the longest, about.000081 cm.; the violet, which is the most refracted, is the shortest or.000033 cm. It is customary to speak of seven colors in the solar spectrum--red, orange, yellow, green, blue, indigo, violet. It is now known that these seven may be made by properly combining red, green, and violet. The primary colors then are red, green, and violet. Between the extremes there are thousands of wave-lengths which cause these colors to shade into each other "in an endless number of shades. The color of light then depends upon its wave-length, while the color of a body depends upon the color of light it reflects. If a body reflects only red and absorbs all other colors it is red. A piece of glass so colored that it will only transmit blue light is blue. Some artificial lights are lacking in one or more colors. When this is the case, objects will not appear to be their correct colors under these lights. For instance, the mercury vap...