Abstracts and reviews
1907
Journal of Geophysical Research
4 B S TR M C TS .,4 _/VD R oe VIE I, VS SCHMZ'D7", "4DOL?'. THE SEDDZ, V OBSER 3oe., 4 G.N'E TO GR M Pt]. • These instruments were recently constructed by Toepfer for the magnetic observatory in Seddin, an auxiliary station ofthe Potsdam Observatory. They represent the most modern type in the remarkable evolution whict• magnetic instruments have undergone in recent years. They are based on the general principles of the Escenhagen magnetdgraph, but are larger, more fully provided with fine
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... ments to ai(t in convenient and exact setting, and contain certain novel features of considerable interest. As in the Eschenhagen instruments quartz suspensions are used for the declination and horizontal intensity variometers, while the vertical intensity variometer is a magnetic balance of special construction. A system of control magnets is permanently mounted on each instrument. As the instruments are not adequately protected from temperature changes the problem of temperature compensation is exceedingly important. By means of the method of Eschenhagen a resultant temperature coefficient sensibly equal to zero has been attained. At the same time it is possible to assign to each instrument any desired sensitiveness. In general, it may be said that the base of each of the instruments is provided with freedom of adjustment over a certain range in either a horizontal or vertical direction in order that the spots of light may be accurately focused and set. :Each has a fixed mirror and two movable mirrors making a small horizontal angle with each other to double the range of registration. These are all at the same height so that the resulting spots of light are devoid of parallax. But in addition the range of each instrument is increased many fold by the use of an inclined movable mirror. The light reflected obliquely upward from this is again reflected onto the recording cylinder by the use of an inclined fixed mirror. Thus as the needle moves the beam of light describes a flattened cone, whose intersection with the drum is nearly a horizontal straight line. But the angular velocity of the beam is much less than that of the magnet, being proportional to the sine of the angle which the normal to the mirror makes with the vertical. A reduced record of magnetic variations is thus obtained from which no conceivable magnetic storm can escape. Each magnet-house contains a Bourdon tube with mirror attached for the registration of changes in temperature. The magnets in the case of the declination and horizontal intensity variometers are one min. thick and elliptical in form, having axes fifty and ten min. in length. %Vith the aid of small graduated circles they can be orientated and 1 ADOLF SCHMIDT. Die rnagnetischen Variations instrumente des Sealdiner Observatoriums. Zeitschrift fiir Instrumentenkunde, May x9o7, pP. x37-•47-87
doi:10.1029/te012i002p00087
fatcat:lakgvbzcxna3jnpx4j7s2ibdfi