242 REPORTS ON INVESTIGATIONS AND PROJECTS, 



with Mr, p. H. Dike, magnetic observer, and Mr. E. H. Bowen, computer, 

 determined the three magnetic elements during September and October at 

 about 70 stations, nearly uniformly distributed over southern Canada between 

 the meridians 70° and 105° west longitude. This region is the one covered 

 by I^efroy in his magnetic survey of 1842 to 1844, and several of his stations 

 were reoccupied, and thus important secular variation data were obtained. 

 These observations will at the same time complete the magnetic survey of a 

 very large quadrilateral of the earth's surface when taken in connection with 

 the magnetic work of the United States Coast and Geodetic Survey ; the 

 work will, moreover, all be based upon one standard. From so large an area 

 valuable contributions to the theory of the earth's magnetism will doubtless 

 result. In connection with the work in Canada a comparison of the standard 

 instruments of the Toronto and of the Cheltenham observatories was also 

 secured. 



The various necessary testing observations and standardizations of instru- 

 ments have been made at Washington and at the Cheltenham Magnetic 

 Observ^atory during the year, mainly by my chief assistant, Mr. J. A. Fleming, 

 and Magnetic Observer D. C. Sowers. 



C. — Magnetic Disturbances. 



The two direct recording declinometers after the design and construction 

 of Dr. W. G. Cady, research magnetician, have been completed. As already 

 reported, one of these instruments has been supplied to the Solar Observatory 

 of the Carnegie Institution of Washington, where it has been in operation 

 since March. The second instrument has been temporarily installed at the 

 office of the Department. An article by Dr. Cady on this instrument will 

 be found in the September, 1906, issue of the journal Terrestrial Magnetism 

 and Atmospheric Electricity. 



D. — Atmospheric Electricity. 



Mr. P. H. Dike, magnetic observer, made an investigation at the Caven- 

 dish Laboratory, under the direction of Prof. J. J. Thomson, on the diurnal 

 variation of the amount of radioactive emanation in the atmosphere. An 

 account of this work has been published in the September number of the 

 current volume of the journal Terrestrial Magnetism and Atmospheric 

 Electricity. 



Mr. J. E. Burbank, magnetician, has completed a report on his atmos- 

 pheric electricity observations made at Battle Harbor, I^abrador, He has 

 also made some observations of the atmospheric radioactivity at Washing- 

 ton, showing the presence of thorium in the air. An account of this work 

 appeared in the June, 1906, issue of the journal Terrestrial Magnetism and 

 Atmospheric Electricity. Mr. Burbank also made some preliminary tests of 

 instruments to be used in atmospheric electricity work at sea. 



