Using the observations of gravity gradients at 191 stations in the neighbourhood of Tôkyô, the writer examined the gravity anomaly in this district. Fig. I and Fig. II indicate the gravity gradients and the distribution of curvature terms which were calculated by means of (1) and (2) respectively. Fig. III is the gravity anomaly-referred to the formula by F. R. Helmert in 1901, (4). Anomaly in this figure can be considered to be very similar to the Bonguer's anomaly in its nature.
In the first paper (This Jour. Vol. 14, No.8) we have described about the long-period seismograph of mechanical registeration with a device of electric amplifying. This instrument was made so as to be usable for the routine work of seismological observation. At present it was installed at the Kôbe Meteorological Observatory. The principle of the instrument now presented is the same as that used in the former case, but some new devices and improvments are made, especially in the part of generating electric current and recording galvanometer circuit. The magnification curve of this instrument for earthquake movements of various periods is obtained and shown in Fig. 4. It varies according to the state of adjustment of amplifier and three curves shown in Fig. 4 are examples in certain states in certain states usually used in actual observations. The curve is very alike to that obtained for Galitzin's seismograph of photographic resisteration. But this instrument has an advantage according to the smallness of the period of recording galvanometer and moreover the magnification can be made very large, probably it will attain for more than 10, 000 if desired for earthquake of a small periods and this is easily done by diminishing the capacity of condensers put in some parts of amplifier. But our present aim does not lie there. For earthquake of ordinary distance the magnification becomes to be about 1, 000 or more. At any rate the writers consider that for the observation of any kind of earthquakes, especially for distant earthquakes, this instrument must play an important rôle. Some examples of seismograms obtained by this instrument are shown in Plate 8, with those of the same earthquakes obtained by Wiechert's 200kg seismograph (V=80) given as a reference. By these seismograms we can clearly see how powerful is our seismograph with electric magnification for the observation of distant earthquakes compared with the mechancally resistering seismographs ordinarilly used.
The effects of thermometer shaft and of radiation on the wet bulb were investigated, and a new psychrometric formula for Assmann psychrometer was derived, that is, e=e"-Bp(t-t") where B=(6.60+0.011t")×10-4 above 0°C =5.8×10-4 below 0°C And it was remarked that the effect of the covering cloth of the wet bulb to the psychrometric constant B is not due to the sorts of the cloth, but is due to the mode of covering of the cloth.
For the purpose of using it as the low tension radio sound battery of the Central Meteorological Observatory, the primary cell: PbO2H2SO4ZnHg is constructed and the factors necessary for the present object are determined experimentally. Vitriol feeder is devised which works, on ascent of the sound, automatically according as the atmospheric pressure decreases (See Fig. 16 & 17 in the text). It feeds concentrated sulphuric acid gradually to the battery liquid and as the result it gives off heat of dilution and protects the battery from chilling and at the same time making for the loss of sulphuric acid in the liquid.
To reply the demand of high tension battery, a new device is given in the construction of the dry battery. According to this device, two kinds of 22.5 volt battery are constructed which weigh respectively 99 and 35 gr and can be discharged respectively for 10.8 and 2.5 hours under the constant load of 5000Ω until terminal voltage drops to 17 volt.