As Professor Church has pointed out, the paste of the Bristol porcelain is of exceptional hardness. It is, in fact, in some specimens as hard as quartz, that is, say, the hardness is equal to 7 in the scale of the mineralogist: the hardness of Oriental porcelain, it will be remembered, varies between 6 and 6·5; the glaze on the Bristol china is about 6 on the same scale. The fractured surface may be described as subconchoidal and somewhat flaky, with a greasy to vitreous lustre. On the Plymouth and Bristol wares, especially on the larger vases, may often be seen, when viewed in a favourable light, certain spiral ridges, the result of the unequal pressure of the ‘thrower’s’ hand. Similar ridges may indeed be observed at times on other hard paste wares, both Chinese and European, and this ‘wreathing’ or _vissage_, as Brongniart long ago pointed out, is the result of the _too great plasticity_ of the clay,--a clay may, in fact, be too ‘fat’ to work well on the wheel. This plasticity, however, would be of advantage to the modeller, especially when working on a very small scale; indeed the delicate floral reliefs in biscuit, on the plaques we have already spoken of, could only have been made from a fine and unctuous clay. How refractory to heat this same paste is, was well proved by the fire at the Alexandra Palace in 1873, when so many fine specimens of English porcelain were destroyed. A biscuit plaque or medallion of Bristol porcelain passed uninjured (by heat at least) through this fire, while the soft porcelain alongside of it was completely melted. The paste, then, of this Bristol ware is remarkable both for its resistance to heat and for its great plasticity. These are both qualities that point to an excess of kaolin in its composition, and this excess is confirmed by analysis. Professor Church found in a specimen of Bristol china 63 per cent. of silica, 33 per cent. of alumina, and only 4 per cent. of lime and alkalis. The percentage of alumina is about the same as that in the hard pastes of Meissen and of Sèvres, but the small amount of the other bases is quite exceptional. A paste of this composition would contain about 65 per cent. of kaolin.