260 CARNEGIE INSTITUTION OF WASHINGTON. 



future special observational work should be undertaken for the 

 solution of such questions as, for example, the effect of locally dis- 

 turbed areas on the secular variation, or the change of the intensity 

 of the Earth's magnetic field with altitude, etc. A critical sifting of 

 the available observatory data has also been begun so as to secure 

 reliable information regarding the secular and other magnetic varia- 

 tions in various parts of the Earth, for use in the construction of the 

 magnetic charts referred to above. Discontinuities are at times 

 found in the observatory series, the cause of which can not always 

 be definitely ascertained from the published reports; thus corre- 

 spondence with the respective directors is necessary. In fact, the 

 present lack of uniformity in method of observation and the need of 

 adequate publication are of serious concern. Unless an observatory 

 has sufficient funds and the required personnel to make possible the 

 prompt and full reduction and publication of its observations, it 

 is very much to be questioned, in the light of all the experience, 

 whether a gain to science will result by the continuation of its obser- 

 vational work. 



The Director has continued, as far as his other duties permitted, 

 the researches on the physical theory of the Earth's magnetism and 

 electric phenomena, as also some investigations respecting the secular 

 variation. He has likewise made a preliminary analysis of the Sun's 

 general magnetic field as disclosed by the published observations 

 at the Mount Wilson Solar Observatory. On May 22 he delivered 

 the Halley Lecture on Terrestrial Magnetism at the University of 

 Oxford, England; also, at Berlin, May 3, and at London, June 4, 

 he gave addresses on the status of the work of the Department. 



Dr. Swann during October devoted his attention chiefly to a study 

 of the observations in atmospheric electricity made aboard the 

 Carnegie, with the special view of ascertaining the directions in which 

 the future work may be improved and amplified. This led to an 

 examination of the theory of the instruments and methods used in 

 atmospheric electric work, several highly important conclusions 

 being reached, of theoretical as well as of experimental interest. 



The magnetic instruments used on land and at sea have received 

 further improvement during the year, such as experience gained in 

 all parts of the Earth has suggested. Nearly all of the instruments 

 used are now being constructed in the workshop of the Department. 



The status of the observational work of the Department to date 

 is shown on plate 13. 



A list of the published papers by members of the Department will 

 be found in the Bibliography. 



The quantity and quality of work accomplished during the year 

 are evidence of the zeal and ability shown by the members of my staff. 



