The author calculated the blackness of a cylindrical brack body with the base, varying specific length from 2 to 10, emissivity 0.25, 0.50 and 0.75, in the accuracy more than three figures.
The numerical calculation was done by the digital computor, “E. T. L. Mark II”, solving the simultaneous linear equations with maximum 27 unknown.
Besides, theoretical upper limit of the blackness of a black body was introduced, and it was compared with the blackness calculated by prof. Z. Yamauti using the specific coefficient of illumination of one term and three terms approximation. As a result, it is pointed out that his calculuted values exceed beyond this upper limit at some points, while author's values remain within it.(Fig. 1)
Moreover, it is suggested that the blackness of a spherical black body, which has a common opening with cylindrical black body, and contacts at the base of it, (Fig. 4) does not exceed that of cylindrical one, though this is nearly equal to that.(Fig. 3)

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The author discusses on the physical meanings of the different definitions of the colour temperature and advises to use in photometry, radiometry and optical pyrometry the definition which is based upon the analogy of the spectral energy distribution curve of the light source to that of the black body and is called as the distribution temperature (Verteilungsternperatur in Germany).
Moreover, he recommends to indicate the distribution temperature of the source with a certan region of wavelength in which the identity of its distribution curve to that of the black body is approved under the considered accuracy.
The author describes a plan to establish the distribution temperature scale, that is, to measure the relative spectral energy distributions of the tungsten ribbon filament lamps choosen as its substandards comparing with a carbon tube black body furnace constructed recently in his Electrotechnical Laboratory.

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The radio noises caused by fluorescent Iamps were investigated in connection with high frequency oscillations in fluorescent lamps, and the mechanisms of oscillations were considered with some experimental results.
Reignition oscillation, whose waveform is irregular and consists of train of fine pulses, is sensitive to external heating of the filament and magnetic field near the cathode. Its frequency spectrum is nearly flat in broadcast band, and its noise level is 62 db (20 W lamp) and 50 db (40 W lamp) respectively in mean value of symmetric quasi-peak voltage at 1 MC. and reduced by 30 db with 0.005μF capacitor connected between lamp terminals.
The twin oscillation, whose waveform is regular and nearly sinusoidal, has the frequency spectrum which is similar to the resonance curve, and in many cases its peak of the spectrum is found in broadcast band.
The high frequency oscillation is observed also in DC discharge, and its cl.arecteristics are same to the twin oscillation. The frequencies of these oscillations vary nearly in proportion to the square root of the lamp current, and are affected by interterminal capacitor.
The cause of reignition oscillation is the fluctuation of ionization in increasing and decreasing period of space charge at transient time on reversing of the lamp current.
The origin of twin oscillation is the oscillatory behavior of ionized medium with suitable accelerating field at the cathode surface, and for generation of the oscillation it is necessary that some feedback conditions from the boundary of the medium to tke cathode are satisfied.

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Methyl mehtacrylate sheet as an illuminating meterial has become by now an essential meterial in moddrn illumination industry and this is primarlly attributable to its high optical efficiency, its excellent heat and mechanical properties and its refined and beautiful look. This article deals with the various properties of methyl methacrylate sheet as an illuminating material and on its utilities.

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