244 CARNEGIE INSTITUTION OF WASHINGTON. 



MAGNETIC AND ALLIED OBSERVATIONS DURING TOTAL ECLIPSE OF SEPTEMBER 



10, 1923. 



A program of desired observations was prepared by Messrs. Bauer and 

 Fleming (see p. 252) and supplied to various expeditions and observatories. 

 The Department established stations for special magnetic and atmospheric- 

 electric observations at Point Loma (within the belt of totality) near San 

 Diego, California, and for magnetic observations at Mount Wilson and at 

 Guatemala City, Guatemala (see p. 238). The director of the United States 

 Coast and Geodetic Survey cooperated in this work by having special observa- 

 tions made at five observatories of that Survey and at a field station near 

 Lompoc, California, within the belt of totality. Professor Joaquin Gallo, 

 director of the National Observatory of Mexico, arranged for special magnetic 

 observations at his astronomical station at Yerbaniz, within the belt of 

 totality, and for a special program by the Mexican magnetic observatory 

 at Teoloyucan. In addition, special observations were made by the Depart- 

 ment observatories at Huancayo, Peru, and at Watheroo, Australia, and the 

 Japanese observatory at Kakioka also had planned to cooperate. Informa- 

 tion was received that numerous other institutions and observatories, includ- 

 ing the Agincourt and Meanook observatories of the Canadian government, 

 would arrange for special observations in accordance with our published 

 program. 



INSTRUMENT WORK AND BUILDINGS.^ 



Classification of work. — The heaviest demand on the instrument shop was 

 for the construction of experimental apparatus, fully one-third of the entire 

 time being given to such work. Something less than one-quarter of the time 

 could be given to the design and construction of new instruments and equip- 

 ment. Improvements and repairs primarily of instruments for field and 

 observatory use and, to a lesser degree, of buildings, engaged something more 

 than one-quarter of the time. Miscellaneous activities, including prepara- 

 tion of detailed drawings, maintenance of stock parts, and renewal of supply 

 of nonmagnetic castings for instruments, and special work, took one-sixth 

 of the available time. \ 



New work. — The principal new instruments and equipment completed 

 during the year and in construction at the end of the year, together with the 

 necessary detailed designs and drawings, included the following: (1) bifilar 

 string electrometers, after Department design, Nos. 19 to 30, completed; 

 (2) construction of two clock, automatic, mercury-contact switches for the 

 earth-current installations at Watheroo; (3) construction of six magnetogram 

 prickers for observatory use to control effectively the shrinkage-correction 

 factors for records from photographic recording devices; (4) construction of 

 two earth-inductor attachments for dip circles; (5) construction and installa- 

 tion of collimating system with controlled shutter for azimuth pier of stand- 

 ardizing magnetic observatory; (6) latern-slide cabinet with special sliding 

 frames for classifying and dust-proof storing of 900 slides; (7) apparatus for 

 assembling of bifilar and unifilar quartz-fiber systems of electrometers; 

 (8) partial construction of three standardized potential-gradient apparatuses 

 with photographic registers for observatory use; (9) five earth-inductor 

 attachments for theodolite magnetometers in stock were begun to make it 

 possible in future to discontinue use of dip circle in favor of the earth inductor, 

 except in Arctic and Antarctic regions, where the dip circle is more con- 

 venient for determination of intensity and declination than the magnetometer 

 and less subject to uncertainty for the determination of inclination than in 

 the lower magnetic latitudes. 



^ From reports of J. A. Fleming, asst. director, and of C. Huff, foreman of instrument shop. 



