TRANSCRIBER'S NOTE: In transcribing this book, the proofreaders found and corrected several minor typographical errors which did not affect the sense of the text. In the caption to Figure 541, the equation for the voltage of a Weston cell at different temperatures was missing a digit "1" and this has been corrected. There is a reference to a Figure 619 but no such figure exists in the original text. There are references to a Figure 119 and a Figure 443; these presumably exist in one of the preceding volumes of the series. Throughout, the use of italic type is indicated by _underscores_. In equations, superscripts are indicated by a caret and braces, as in X^{2} for "X squared". Subscripts are indicated by underscore and braces, as in E_{t} to mean "E sub t". THE THOUGHT IS IN THE QUESTION THE INFORMATION IS IN THE ANSWER HAWKINS ELECTRICAL GUIDE NUMBER THREE QUESTIONS ANSWERS & ILLUSTRATIONS A PROGRESSIVE COURSE OF STUDY FOR ENGINEERS, ELECTRICIANS, STUDENTS AND THOSE DESIRING TO ACQUIRE A WORKING KNOWLEDGE OF ELECTRICITY AND ITS APPLICATIONS A PRACTICAL TREATISE by HAWKINS AND STAFF THEO. AUDEL & CO. 72 FIFTH AVE. NEW YORK COPYRIGHTED, 1914, by THEO. AUDEL & CO., New York. Printed in the United States. TABLE OF CONTENTS GUIDE NO. 3. GALVANOMETERS 431 to 464 Action of compass needle--simple galvanometer--difference between galvanoscope and galvanometer--sensibility--action of short and long coil galvanometers--classes of galvanometer--astatic galvanometer--tangent galvanometer--graduation of tangent galvanometer scale--table of galvanometer constants--mechanical explanation of tangent law--sine galvanometer--table of natural sines and tangents--comparison of sine and tangent galvanometers--differential galvanometer--ballistic galvanometer--kick--damping effect--use of mirrors in galvanometers--lamp and scale--damping--D'Arsonval galvanometer: construction, operation; uses--galvanometer constant or figure of merit--shunts. TESTING AND TESTING APPARATUS 465 to 536