262 



Reports on Special Researches 



No. 27.-WASHINGTON, D. C. (DEPARTMENT OF TERRESTRIAL MAGNETISM). 



A -v'ery large mimlier of comparisons and experiments has been made by the Depart- 

 ment of Terrestrial Magnetism at \^"ashington, District of Columbia, since its establish- 

 ment on April 1, 1904. During the period 1905-13, the observations were made chiefly in 

 two small non-magnetic huts built on a bluff overlooking the Zoological Park, in close 

 proximitj' to the quarters in the Ontario Apartment House first occupied by the Depart- 

 ment. However, since the purchase of the present site in 1913 and the erection of special 

 buildings during 1913-14, exceptional facilities are possessed by the Department for stand- 

 ardizing magnetic instruments and for carrying out the various experimental problems 

 ensuing from such work. The present site of the headquarters of the Department of 

 Terrestrial Magnetism is one singularly free from the local magnetic disturbances so 

 prevalent in the city of Washington and vicinity. (Fig. 4, Plate 13, shows a rear view of 

 the 3 observing houses.) 



The following specimen comparisons (Tables Nos. 27 A, 27 B) between C. I. W. mag- 

 netometers Nos. 3 and 5 at Washington in 1907-08 will be of interest in view of the 

 fact that magnetometer No. 5 was used as the intermediar.y instrument for obtaining com- 

 parisons in 1908-10 between the C. I. W. standards and those at Helwan, Kew, Pola, 

 Potsdam, and Tiflis. (See also Tables 30 A, 30 B, 30 C, 30 D, pp. 268-269.) 



'All values are referred to station ^ni.' -Am = Cm +17. '9 (serie-s I); Am = Cm +19'.2 (series II). 

 ^These are the values obtained with C. I. W. No. 3 standardized. 



