There are cases in which interference colour appears on the surface of the glass exposed to the air. It seems that the glass surface is attacked by the water vapour, and is altered in various ways. These facts are presumably related to the problem of the water vapour condensation on the glass surface. As for the scratches on the glass surface, special condensation patterns are observed.
We have used the polished surface of the various optical glasses because homogeneous surfaces are obtained easier than other cases. We have observed mostly with naked eyes and in some significant cases (for example, on the various scratches of the glass surface) with the help of microscope, the appearances of dew drops and their growths on the altered portions on the optical glass effected by print of finger patterns, metallic soap films, synthetic resin films, interference films on the glass surface caused by immersing in the HNO₃ at various lengths of time, or scratches in various ways, etc.
The conclusions of the observations are summarized as follows:
(1) Dew drops appear earlier and develop faster on the print of finger patterns (Fig. 2, 3) and metallic soap films (Fig. 4, 5, 6) than on the glass surface proper.
(2) Dew drops appear slower on the resin film (Fig. 7, 8, 9, 10) than on the glass surface proper.
(3) Dew drops appear in most cases earlier and develop faster on the interference films than on the glass surface proper, but it seems difficult conclude so because of the complexity of its surfaces.
(4) Dew drops appear earlier and develop faster on the latent scratches (G. D. D. Growth of dew drops 1, 2, 3, 4) and on the scratches by the razor blade (G. D. D. 5, 6) than on the intact glass surface.
(5) As for the scratches, condensation patterns will differ case by case.

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As a continuation of the author's previous paper on “The Effect of Grain Size Distribution”, the effect of chamotte content on the physical properties of pot materials was studied for fortyfive different pot materials in which the content of each one of nine differently grain-sized chamottes was changed from 35 to 55 per cent by the step of 5 per cent, and the following results were obtained.
1) While the content of the chamotte has greater effect than its grain size on the fluidity or drying characteristics of pot materils, the effect of the latter is, on the contrary, greater than the former on the firing or spalling or spalling natures.
2) The effect of the contents of water and dispersing agents in slips used for casting is observed not only on drying but also on firing characteristics, and the more are the contents the more the textures of dried or fired materials become rough, and when the contents of water and dispersing agents are the same, the densest texture is obtained for the clay content of 50 per cent.
3) About 80 per cent of the spalling resistance of the pot materials, at temperatures when the glass batch is thrown into the pot or when the pot is pulled out of the furnace after the glass is melted, is affected by their porosity and the more porous they are, the more resistant they are to spalling.
4) In the range of the present experiment, the pot material containing 35 per cent clay has the best spalling resistance and when the clay content is increased as much as 40 per cent, the resistance is suddenly decreased, and further increase of the clay content causes slow increase of the resistance.
5) No distinct relationship was found between the content of the chamotte or the content of the clay used for pot materials and the physical properties of dried and burned materials.

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Changes of refractories, both silica and grog brick, after a long period of service in a by-product coke oven were studied. Sample bricks were taken from different parts of the oven. As they showed layered structure, chemical analysis, microscopic examination, estimation of mineral composition, determination of density, porosity and of water absorption were made on each layer. The results are summarized as under.
(1) Silica brick from the centre of coking chamber wall: In the first (hotest) layer, all of quartz has been converted into tridymite of lath-shape habit, whereas cristobalite content increases gradually towards the coke side (lower temperature layers). The impurities, such as iron oxide and lime, seem to have migrated from both of coke and flue side towards the mid-layer, where they reach maximum amount.
(2) Silica brick from oven door (jamb brick): Chief mineral composition is very much like to that of the brick from the wall, except that the impurities are concentrated on the flue side. Those impurities have come from flue side, whereas hitherto only those from coal ash were noticed.
(3) Grog bricks from the roof and sole of the coking chamber: The impurities are concentrated on those surfaces which are facing to coking chamber. There are many large cracks on the surface.
(4) Sulphur and carbon contents are slight in silica bricks. Sulphur seems to occur in forming ultramarine.

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Eight American and five Japanese chromlte series refractories were tested. Data for chemical compositions, physical properties, mechanical strength, thermal changes, and bursting expansion are given. A procedure for the separation of chrome spinel grains from chromite series refractories by flux, KOH+NaOH+K₂CO₃+Na₂CO₃(6:4:5:5), is described and then chemical compositions, heating curves by means of thereto-balance, and solid-solution compositions of chrome spinel grains are written.

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