Following table are given the annual values of the magnetic elements in 1929 as derived from 41 determinations:--
Declination (West) 0°43.5′ Dip (North) 30°38.7′ Horizontal Force (C.G.S. unit) 0.37481 Vertical Force (C.G.S. unit) 0.43565 Total Force (C.G.S. unit) 0.22206 (?) likely should be placed under "Horizontal Force" or another appropriate column, but as per the original, it is left here.Photographic registration of the variation of magnetic Declination, Horizontal Force, and Vertical Force was maintained at Au Tau throughout the year, except from May 30th to August 30th, during which period alterations were made in the magnetograph house, with a view to securing greater temperature insulation. During the progress of these alterations the disposition of the registration apparatus and lights of the Declination variometer was rearranged, in order to obtain a greater scale value: It is now 5.53 inches for 1°, in place of 2.80 inches.
The measurement and tabulation of the magnetograms has not been commenced, as the records are not yet satisfactory. The trace of the H.F. variometer has shown a persistent creep throughout the year, in a direction signifying increased moment of the magnet, or decreased torsion couple. As it was thought that the shellac joints of the suspension had possibly become soft and yielding, on account of the high temperature experienced during the summer months, they were replaced by solder. The creep continues however, and further investigation as to its origin is necessary.
The frequent adjustments of the V.F. thermograph on the V.F. variometer, necessary on account of its very open scale value, produced disturbances of the V.F. scale value, and the suspension was eventually broken during one such adjustment, in May, prior to the commencement of the alterations to the building. The suspension was repaired and registration resumed in August, after an arrangement had been fitted whereby adjustments could be effected to the thermograph without opening the instrument case. The V.F. record is not yet satisfactory however, and at the end of the year, experiments were again in progress to determine what scale value should be adopted.
Much difficulty has been experienced in obtaining suitable and sufficiently economical registering lights, which could be fixed with the necessary rigidity; but satisfactory registration is now being obtained with a frosted strip-light lamp in a firmly fixed brass cylindrical cover in which a fine vertical slit is cut. No condenser is necessary with this method.
The Chinese attendant at Au Tau is changing the photographic sheets satisfactorily and keeping the batteries charged, but he cannot cope with emergencies when they arise. It is necessary to send an officer from the Observatory, a distance of 27 miles. This occasionally causes delay in rectifying faults and consequent loss of register.
-F 11
following table are given the annual values of the magnetic elements in 1929 as derived from 41 determinations:--
Declination (West)
0.43.5
Dip (North)
30.38.7
Horizontal Force (C.G.S. unit) Vertical Force (C.G.S. unit)
0.37481
0.22206
0.43565
Total Force (C.G.S. unit)
Photographic registration of the variation of magnetic Declination, Horizontal Force, and Vertical Force was main- tained at Au Tau throughout the year, except from May 30th to August 30th, during which period alterations were made in the magnetograph bouse, with a view to securing greater tem- perature insulation. During the progress of these alterations the disposition of the registration apparatus and lights of the Declination variometer was rearranged, in order to obtain a greater scale value: It is now 5.53 inches for 1°, in place of 2.80 inches.
The measurement and tabulation of the magnetograms has not been commenced, as the records are not yet satisfactory. The trace of the H.F. variometer has shown a persistent creep throughout the year, in a direction signifying increased moment of the magnet, or decreased torsion couple. As it was thought that the shellac joints of the suspension had possibly become soft and yielding, on account of the high temperature experienced during the summer months, they were replaced by solder. The creep continues however, and further investigation as to its origin is necessary.
The frequent adjustments of the V.F. thermograph on the V.F. variometer, necessary on account of its very open scale value, produced disturbances of the V.F. scale value, and the suspension was eventually broken during one such adjustment, in May, prior to the commencement of the alterations to the building. The suspension was repaired and registration resumed in August, after an arrangement had been fitted whereby adjust- ments could be effected to the thermograph without opening the instrument case. The V.F. record is not yet satisfactory how- ever, and at the end of the year, experiments were again in progress to determine what scale value should be adopted.
Much difficulty has been experienced in obtaining suitable and sufficiently economical registering lights, which could be fixed with the necessary rigidity; but satisfactory registration is now being obtained with a frosted strip-light lamp in a firmly fixed brass cylindrical cover in which a fine vertical slit is cut. No condenser is necessary with this method.
The Chinese attendant at Au Tau is changing the photo- graphic sheets satisfactorily and keeping the batteries charged, but he cannot cope with emergencies when they arise. It is necessary to send an officer from the Observatory, a distance of 27 miles. This occasionally causes delay in rectifying faults and consequent loss of register.
M
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