266 REPORTS ON INVESTIGATIONS AND PROJECTS. 



nal secular variation system. This sj-stem plays an important part 

 in the secular variation of the magnetic declination. 



(2) The secular variation of the earth's magnetism is caused not 

 only by a change in the direction of the magnetization, but likewise 

 by a change in the intensity of magnetization. 



These results, if true, are of such importance that it is essential they 

 be tested at the earliest possible moment with the aid of new and more 

 comprehensivel}' distributed data. Accordingly the selection and 

 establishment of a series of secular- variation stations over the globe, 

 at which observations shall be made at regular intervals of about five 

 years, has been undertaken and observations have been begun as 

 related under "Field work." 



Investigation II. — Discussion and publication of the data 07i the 

 magnetic perturbations observed during the eruption of Mont PelS, 

 Martinique, igo2. — Good progress has been made with this investiga- 

 tion under the direction of Mr. J. A. Fleming, magnetician in charge. 

 It is hoped that the completed manuscript can be submitted for publi- 

 cation before very long. Principal assistance was rendered in this 

 work by Dr. S. Tetsu Tamura and Mr. A. H. Homrighaus. 



Investigation III. — A general study of the laws of the ditirnal 

 variation to serve as the basis for determining corrections atid their relia- 

 bility for the reduction of field observations. — A paper under this head 

 on the ' ' Diurnal motion of a free magnetic needle ' ' will soon be 

 ready for publication. It will contain results helping to elucidate the 

 dependence of the diurnal variation at a given station upon latitude 

 and longitude. 



Investigation IV. — Special invcstigatioii of magnetic storms with 

 the view of dctermiriing a workijig method for the disctissioii ajid analysis 

 op stichfltictuatio7is. — These studies are being conducted, since January , 

 under the direction of Prof. Adolf Schmidt, in charge of the Potsdam 

 Magnetic Observatory, with the aid of funds to the amount of $750 

 supplied, with the approval of the Executive Committee, by the 

 department. Professor Schmidt has access, for this purpose, to 

 copies of notable magnetic storms, received from cooperating mag- 

 netic observatories over the entire globe. He has made a preliminary 

 report covering the work up to the end of August, from which it is 

 evident that excellent progress has been made. A " first communi- 

 cation • ' will doubtless be ready for publication by the end of the 

 year and will contain the analysis of the fluctuations occurring on 

 two " term " days of the international " polar" year, viz, March 15 



