DEPARTMENT OE TERRESTRIAL MAGNETISM. . 173 



West Indies and Central America. — Mr. W. H. Sligh, newly appointed a 

 magnetic observer, was assigned at the dose of the year to complete the work 

 in these countries begun by Mr. Ault in 1905 and continued by Mr. Fleming 

 in 1907. Mr. Sligh has completed the preliminary arrangements, and for the 

 purpose of securing some additional experience made magnetic observations 

 at some stations in Maryland under the direction of Observer Stewart. He 

 will leave Washington for the West Indies early in November, 1908. 



OFFICE AND EXPERIMENTAL WORK. 



It may be readily appreciated that with such world-wide field operations 

 in progress, as described in the foregoing pages, the time of the office force is 

 largely consumed with executive and administrative matters. Much time has 

 been given to the determinations of constants and corrections for the various 

 instrumental outfits required for land and sea work. As the result of rigid 

 tests made with regard to magnetic impurities in outfits, the corrections of 

 the various magnetometers to an international standard have been reduced to 

 a minimum. The imperfections as they were found could be immediately 

 remedied in the instrument shop of the Department, established in January, 

 the usefulness of which has been amply demonstrated. A great amount of 

 repair and detail instrument work could thus be expeditiously undertaken 

 under direct supervision. The services of Mr. Adolf Widmer were secured 

 as mechanician in charge ; he has shown himself both efficient and capable. It 

 is hoped that before long the Department will be able to make the magnetic 

 instruments required almost exclusively in its own shop, an advantage which 

 every experienced magnetician will readily appreciate. 



Plans and experiments for the construction of special ship instruments, 

 already above referred to under ocean work, are at present in progress. 



In cooperation with the special investigations of the Director of the Mount 

 Wilson Solar Observatory as to the relation between certain solar and terres- 

 trial magnetic phenomena. Dr. W. G. Cady has made some further improve- 

 ments in the direct-recording declinograph installed at the Observatory. 



As in the past, the current observations have been reduced as received in 

 order to promptly correct any defects in instruments or methods. Excellent 

 progress has been made with the preparation for publication of the results of 

 all observations (on land and at sea) thus far made by the Department, and 

 it is hoped that by the end of the calendar year the manuscript for the first 

 volume of Magnetic Results of the Department will be ready for the press. 



Material assistance has been rendered, in cooperation with the U. S. Coast 

 and Geodetic Survey, in the completion of the special publication by the 

 Director on the results of the magnetic survey of the United States and mag- 

 netic maps for January i, 1905; this publication is now in the hands of the 



