The paper deals with some problems of lunnar tidal anlyses of ionospheric height, which are treated from the standpoint of mathematical statistics. The semi-amplitude of lunar semi-diurnal tide of Z_mF₂ (height of maximum electron density of F₂ region) analyzed from Japanese data is tested by statistical hypothesis and its results are described. Next the error caused by a rough scaling of height is estimated in connection to scaler's skill (or carefulness), and the results are given.
Some statistical measures are introduced for the criterion of the validity of analyzed results in the above treatments, that is, the level of significrnce for the former case (test of statistical hypothesis by non-parametric method) and the coefficient of confidence for the later case (estimation of error).

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We made a simultaneous observation of the electric potential gradient and the space charge under the volcanic smoke of the new crater of Volcano Azuma in Fukushima-prefecture from August 13th to 19th 1950, to investigate the charge distribution in the volcanic smoke. The remarkable points which we obtained by the analysis of this observation are:
(i) The charge of the smoke of Volcano Azuma is positive, and the density of which is estimated at about 5 e. s. u. /m³ near the center of the smoke.
(ii) A thin layer of the negative charge is induced around the cylinder shaped smoke. The density of the induced charge is about 1/10 of that of the positive charge near the center of the smoke.

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In order to estimate the influence of the diurnal variation of the atmospheric temperature on that of cosmic ray intensity, we investigated the bihourly data of cosmic ray intensity at Huancayo and aerological data at San Juan. As the mean atmospheric temperature, the altitude differences between 100mb. and 1000mb. levels were used. We ascertained that the amplitude of the diurnal change of cosmic-ray intensity at Huancayo exceeded 0.5% at least (i. e. twice that of the observed value), if the temperature effect was taken into accounts.

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