The most predominat causes of the wide varieties of unfired kaolins in their physical properties seem to depend on the degree of crystallinity and particle size.
For the sake of more reliable deduction of the degree of crystallinity and particle size of kaolins, admixtures were made and their influences on the D. T. A. curves were examined. On admixing an inert substance, only a diluent effect was found in thermal peaks of kaolins, whereas in the case of the mixtures of 2 sorts of kaolins, a mutual influence between the each original exopeaks was detected. The results obtained are summarrized as follows.
(1) In accordance with the increasing replacement of kaolins by α-Al₂O₃, the interval between the endo- and exopeak became wider. By the same degree of the replacement, the shifting of exopeak towards higher temperature amounted to the 1/10 order of that of the endopeak towards lower temperature.
(2) It seemed that the “slope ratio” differed with the kaolin content. The interval between the starting and top temperature of endo-peak largely changed with the kaolin content, however, the interval between the top and final temperature of the peak was not so much affected.
(3) The complicated shape of exopeak which appears in rare cases on the D. T. A. curve of a kaolin seems to be caused by an ifluence of acompanied montmorillonite or other sort of kaolin having an exopeak which differs more than about 30°C from that of the main component mineral.

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In a previous paper one of the authors, A. Naruse, formulated the relation between the dimensions of the throat of a glass tank furnace and the maximum velocity of the current passing through it. And the present one contains the result of a series of model experiments carried out in order to built up a sound experimental background for the theory postulated before, and if necessary, to modify it.
A transparent plastic model throat, 6cm long, 5cm wide, and variable height 1-4cm, having the dimensions as a whole which satisfy the similarity conditions to actual tank as far as possible, was used for the experiments. The model was immersed in a water bath which was composed of three compartments so that the temperature of either one of both end-sections may be fixed at a desired point. Furthermore, in order to set up the necessary temperatures at the principal points, the melting chamber was heated electrically with a hot plate, while the working chamber was cooled with water.
As a liquid medium was used 83% glycerin, and as the traces for observing the flow of liquid were used the coloured oil droplets having the specific gravity well matched with that of the medium. At regular time intervals a fine line of coloured oil was drawn through the liquid, which immediately afterwards disperse into minute droplets. The velocity of flow at every level was determined from the photographic records taken at regular time intervals. The observations were carried out under the conditions both with and wothout pull.
A fairly good agreement of the experimental values with those calculated by Peychès' formula was proved. And, if the correction for the friction at the side walls was introduced, the agreement became excellent.
As long as the throat is not too high the velocity distribution in existence of pull was also in good agreement with the theory.
The co-existence of the convection and the pull currents in a throat makes the forward current stronger, while it makes the backward current to run down gradually until it finally vanishes.
This limited velocity Wc may be expressed as
Wc=1/72⋅ρ₀ρbgk/η⋅Δθ/l⋅fh⁴
When the height of the throat is changed keeping the pull velocity constant the limiting height having the same meaning as above may be represented as follows:
f^1/4h_c=2.91(Wηl/ρ₀ρbgkΔθ)^1/4
The symbols used in those equations are referred to the table of nomenclatures in the text.
From the technological point of view the authors maintain their opinion that both figures give the corresponding optimum values which reduce the velocity of erosion of refractories to the minimum.

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The construction and the operation of the automatic recording dilatometer which was developed for measuring the thermal expansion of glass is described. The sample, 10cm long and 1.5-2.0mm in diameter, was heated at a constant rate, and the temperature was recorded by an automatic temperature recorder. The expansion of the sample was magnified by an optical lever having the effective length of about 5mm, and was traced by a tracer mechanism. This mechanism drived therecording chart of the recorder, and as the result, the expansion curve of the sample was drawn on the chart.
Several improvements were also made on the dilatometer to increase its accuracy.
Results of the measurements for three kinds of glass are described briefly.

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[in Japanese]

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