File:A text-book on chemistry. For the use of schools and colleges (1866) (14796329963).jpg

Identifier: textbookonchemi00drap (find matches)
Title: A text-book on chemistry. For the use of schools and colleges
Year: 1866 (1860s)
Authors: Draper, Henry, 1837-1882
Subjects: Chemistry Physics
Publisher: New York, Harper & brothers
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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seen in the figure,and the oiled silk is shownat c / d is the prime con-ductor, usually a cylinderwith rounded ends, made of thin brass, and e its insu-lating support. Of these machines the plate is commonly the mostpowerful. It is more liable to be broken than tl^e cyl-inder, from the disadvantageous way in which the pow-er to turn it round is applied. To bring an electrical machine into activity, it mustbe thoroughly dried, but a plate machine should neverbe set before the fire to warm, or it will almost certain-ly crack. The rubbers are to be spread over with alittle Mosaic gold or amalgam of zinc, and the stem ofthe conductor made dry. If the rubbers of the machineare not in connection with the ground, there must be achain hung from them to reach the table. Then, whenthe instrument is in activity, on presenting the ringer Describe the cylinder machine. Which is the best? How is anelectrical machine prepared for action ? What occurs on presentingthe finger to the prime conductor ?
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128 ELECTRICAL EXPERIMENTS. to the prime conductor, a succession of sparks is emit-ted, attended by a crackling sound. A great many beautiful experiments may be made bythe aid of this machine. They are, for the most part,illustrations of the luminous effect of the spark, attrac-tions and repulsions, and certain physiological results,as the electrical shock. If small pieces of tin-foil be pasted round a glass tubeFig. 89. in a spiral form, as shown in Qg?s^/v\/s*ALA*fA Fig. 89, a b c, distances of thea & c twentieth of an inch interven- ing between, and the ends of the tube terminated byballs, on presenting one of these balls to the prime con-ductor, and holding the other in tjie hand, as the sparkpasses it has to leap over each interstice between thespangles of tin-foil, and exhibits a beautiful spiral lineof light. By pasting the tin-foil on apane of glass in such a wayas to direct the spark prop-erly, words may be writtenin electric light, as shown inFig. 90. As the electric spa

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