DEPARTMENT OF TERRESTRIAL MAGNETISM. 235 



track,* passing through the central part of the Pacific Ocean, along 

 which magnetic data were obtained, as was the case prior to the year 

 (1905) when our ocean work began, there are now about 8 north-and- 

 south tracks and about the same number running east and west. Not 

 only can accurate magnetic charts for the use of mariners be con- 

 structed now, but also the requisite charts may now be prepared for 

 investigation of some fundamental outstanding scientific questions 

 concerning the Earth's magnetism. 



For the North Atlantic Ocean we also now have information along 

 a suflBcient number of tracks to meet the mariner's practical demands 

 and to assist in the solution of scientific questions. However, for the 

 South Atlantic and Indian Oceans, additional cruises would have been 

 desirable and could have been accomplished by this time had it not 

 been for the interruption caused by the war. 



As soon as the Carnegie's work may be resumed, it will be necessary 

 to undertake further cruises, especially in the South Atlantic and 

 Indian Oceans, and to secure crossings of the tracks in all of the oceans 

 for the purpose of determining the changes to which the Earth's 

 magnetic state is continually subjected. Since in the future cruises it 

 will probably not be necessary to make the magnetic observations as 

 intensively as in the past, it is hoped that there may be opportunity 

 to take up other fines of ocean investigations which may again promise 

 results both of practical utility and of scientific value. 



ATMOSPHERIC-ELECTRIC WORK. 



This work has been continued on the Carnegie, as have also the 

 investigations and observations at Washington. Furthermore, special 

 observations were made during the total solar eclipse of June 8, 1918, 

 the stations being Lakin, Kansas, in the belt of totaUty, and at Wash- 

 ington, where the magnitude of maximum obscuration of the Sun 

 was 74 per cent. For an account of the work under this head, see 

 pages 238-239. 



LAND MAGNETIC WORK AND ECLIPSE OBSERVATIONS. 



The conditions caused by the war made it necessary to restrict the 

 magnetic survey of land areas to the following work, all of which was 

 successfully accompHshed : 



1. Africa. — Observer H. E. Sawyer led an expedition along the Upper 

 Nile, through the interior of Eritrea to the port of Massawa, and 

 thence partly along the Red Sea and partly along the Nile, arriving 

 finally at Helwan, near Cairo, where he compared the magnetic 

 instruments used by him with those of the British magnetic 

 survey of Egypt. On his homeward journey, via the Pacific, he 

 expects to reoccupy some of our previously-established stations. 



*Thus Capt. Ettrick W. Creak, in his letter to the Institution, in which he indorsed the project 

 of the Department of Terrestrial Magnetism, said: "The North Pacific Ocean is, with the excep- 

 tion of the voyage of the Challenger, nearly blank as regards magnetic observations." 



