abstracts: terrestrial magnetism 17 



for the observatories in the Sun-Ht portion of the globe, and seems to 

 be reversed for the observatories in the night portion, judging from the 

 place where the corresponding solar observations are made. This is 

 being looked into further. 



In the discussion of magnetic disturbances we may have to dis- 

 tinguish between two broad classes: 



(1) The curvilinear, the more prominent as far as general magnitude 

 is concerned, occurring practically over the whole Earth at the same 

 time, seemingly initiated by such radiations or streams of charged 

 particles which are deflected from a straight path, when they come 

 under the influence of the Earth's magnetic field, as to pass around 

 and behind the Sun-lit portion of the Earth. 



(2) The rectilinear, occurring practically only over the portions of 

 the Earth reached by the straight-line, or ordinary, radiations from 

 the Sun. L. A. B. 



TERRESTRIAL MAG^YH^WM.— Regarding improvement of appliances 

 for measurement of the Earth's magnetic elements by magnetic and 

 electric methods. (Progress Report.) L. A. Bauer, Terr. Mag., 

 19: 1-18. 1914. 

 The instruments for magnetic measurements, employing distinctively 

 magnetic methods, have now reached the requisite stage of perfection 

 for meeting the practical requirements, both on land and at sea. How- 

 ever, the desire is to devise and try out new methods, as, for example, 

 those based on electrodynamic or electric principles, with a two-fold 

 object in view: (1) to obtain, more expeditiously than is possible with 

 the type of magnetometer now in general use, a magnetic measurement 

 within the relative accuracy required for a successful study of the 

 magnetic variations; (2) to obtain, another control, by means of a dis- 

 tinctively different method, on the absolute accuracy of the present 

 magnetic standards. The present report summarizes what has been 

 done thus far with respect to improvement of the appliances and 

 methods for the measurement of the terrestrial-magnetic elements and 

 what is still further to be undertaken. 



In all of the Department's types of magnetometers, the magnet house 

 is of wood. Furthermore, every instrume^t is as nearly as possible 

 an independent or absolute one, i.e., all the various constants can be 

 absolutely determined. It is shown that, as the result of numerous 

 comparisons, it would seem safe to conclude that the H, or horizontal- 

 intensity, standards of Kew, Potsdam, and Washington (Department 

 of Terrestrial Magnetism) give an absolute accuracy within one part 



