Isochromatic Lines
in optics, colored rings appearing when a pencil of polarized light is transmitted along equilibrium, by which, when slightly dis- property appertaining to all systems in and, after passing through a plate of tourmaline, finally reaches the eye.
ISOCHRONISM a property appertaining to all systems in equilibrium, by which, when slightly dis- (is-ōk'ron-ism), instance, is allowed to vibrate till it sulting are all performed in the same time, or so nearly in the same time rests, it will be found that no perceptiimperceptible. When a pendulum, for instance, is allowed to vibrate till it rests, it will be found that no perceptible difference exists between the vibrations of longer or shorter extent, the same number of vibrations being made in the same length of time. Again, in blow on the pianoforte key and a gen- in the pitch of a note made by a smart the finest ear cannot detect any difference weights. tle touch; yet a very small difference in blow on the pianoforte key and a gentle touch; yet a very small difference in the number of vibrations per second would be perceptible to the ear.
ISOCRATES (i-sok'ra-tēs), orator and rhetorician; born in Athens in 436 B. c. He was carefully educated, Socrates having been of the number of his preceptors; and at an early age was a Greek its graduates. The ages have spared to quence of the exceptional attainments of which soon filled all Greece, in conse- opened a school of oratory, the fame of distinction in public life. He therefore hope he may once have entertained of distinction in public life. He therefore opened a school of oratory, the fame of which soon filled all Greece, in consequence of the exceptional attainments of its graduates. The ages have spared to us 21 of his compositions, rhetorical and espistolary. He is best represented by the discourses known as the "Areopagiticus" and the "Panegyricus." GONIC LINES, lines of equal force, equal inclination, and equal declination, netism of the globe as exhibited at the