DEPARTMENT OF TERRESTRIAL MAGNETISM. 313 



during the period of a solar eclipse. This magnetic effect, and the one which 

 may be shown with regard to the change in the electrification of the atmos- 

 phere dm'ing the eclipse, are of special interest in connection with the wireless- 

 telegraphy experiments conducted during the eclipse at numerous stations 

 along the coasts of Africa, Europe, and America, under the direction of Dr. 

 W. Eccles, of London. Respecting the latter observations, some interesting 

 results have been received by him, indicating that the distance of transmission 

 of signals sent from Ascension Island, in the South Atlantic Ocean, was 

 increased during the time when the eclipse-shadow was between the trans- 

 mitting station and the receiving station. 



There was a steady shght decrease in temperature from 12^ G. M. T., 0.7 

 minute after the first contact, to 12.7^ G. M. T., and then a more rapid decrease 

 until 1^^ G. M. T., when the minimum temperature of 79.4° F. was reached. 

 This time (li^) was approximately 0.4^ later than the middle time of totaUty. 

 The increase in temperature after 14'' was rapid, the maximum 82.7° F. being 

 reached at 14.9^ G. M. T. The hygrogram for May 29 showed the following 

 effect: the humidity, which was 71 per cent at 12^ G. M. T., steadily increased 

 to 78 per cent at 14'' G. M. T. There was a more rapid decrease from 14** 

 G. M. T. to IS'' G. M. T., when the humidity was 66 per cent. The maximum 

 humidity, therefore, occurred at 14'', or approximately 0.4 hour later than the 

 middle time of totahty. The barogram showed nothing marked during the 

 time of the echpse. 



Note on a string galvanometer for use on board ship. J. A. Fleming. Terr. Mag., vol. 24, 

 29-32 (March 1919). Washington. 



This note describes a string galvanometer constructed in the instrument 

 shop of the Department. It is of the type originally developed by Professor 

 Einthoven, of the permanent-magnet air-damped pattern. The magnetic 

 field is produced by a laminated magnet consisting of 5 permanent horseshoe 

 magnets. The string element is a fine quartz fiber coated with silver or plati- 

 num by the method described by Professor H. B. Williams;^ the fiber is sol- 

 dered to 2 cyHndrical copper lugs mounted in standards capable of adjustment 

 by which the fiber may be centered in the air-gap between the soft-iron pole- 

 pieces. The tension of the fiber is regulated by means of a screw operating 

 through the end-supports on threads of slightly different pitches. The arrange- 

 ments are such that the fiber of any length between 93 mm. and 120 mm. may 

 be used. Suitable cover plates and caps are provided to exclude dust and air- 

 currents. 



The deflection of the fiber produced at right angles to the magnetic field 

 by the passage of a current through the galvanometer may be observed 

 directly on the scale in the eyepiece of a microscope suitably mounted, or by 

 projecting the image of the fiber on a glass scale by means of a beam of Hght 

 passing through the microscope and an optical condenser and suitably mounted 

 prisms on the opposite side of the instrument. The mounting for the gal- 

 vanometer is such that it may be set up with the fiber either in a horizontal 

 or in a vertical position. 



When used on shipboard it was found that vibrations, for example those 

 from the engine, could be practically eliminated by suspendmg the galvano- 

 meter by strong rubber bands. 



Auxiliary tables to facihtate revisions of field magnetic observations. H. W. Fisk. 



It has hitherto been customary to complete the reduction of time records 

 to deduce the clironometer rate required for the revision of the oscillation 

 observations. This has often delayed revisions unduly, since the chronometer 



^ On the silvering of quartz fibers by cathode spray, Physic. Rev., ser. 2, voL 4, pp. 517-521, 1914. 



