And here, before ending, we may for a moment return to what is, perhaps, the crucial point of all in the composition of true porcelain--for it is one that has a radical influence both on the technical and on the artistic side. The first question we must ask when inquiring into the composition of any specimen of porcelain is this--What proportion of kaolin enters into its composition? Or if it is a matter of the primary constituents of the paste--What is the percentage of alumina that it contains? Now we may consider the composition of kaolin, after removing the water, to be silica 54 per cent. and alumina 46 per cent., and the nearer the composition of our porcelain approaches to these figures, the greater will be its hardness, its resistance to fire, and the greater also the plasticity of the paste--the greater in fact will be what we have called the ‘severity’ of the type.[255] Now for the other component of porcelain, the petuntse or china-stone. The composition of this material differs widely, but let us take the mean of some analyses of Cornish stone. On this basis we may take silica 72 per cent., alumina 18 per cent., other bases 10 per cent., as our type. The result of adding such a material to our kaolin will be to increase the percentage of silica and of the ‘other bases,’ and to diminish the percentage of alumina in the resultant mixture. Our paste now becomes less plastic and the resultant porcelain more readily softened by heat, but at the same time less hard. So far every one would be agreed. But the question now arises, are we to attribute this increased fusibility to the higher percentage of the other bases (these are, in the case of European porcelain, practically lime and potash), or in a measure at least to the increased amount of silica in the paste? We have here three variants, the silica, the alumina, and the ‘other bases,’ and the case is therefore somewhat complicated. I think, however, that the careful examination of any table giving the composition of various types of porcelain would show that up to a certain point an increase in the amount of silica promotes a lower softening-point in the paste, and this in cases where there is no important change in the proportion of the ‘other bases.’ I will illustrate this by comparing the composition of the severe hard paste of Sèvres on the one hand with an analysis of a mild type of Chinese porcelain on the other:-- Sèvres hard paste (1843). Chinese porcelain. Silica, 58 per cent. 70·5 per cent. Alumina, 34·5 ” 21 ” Other bases, 7·5 ” 7·5 ” No doubt, if the percentage of silica is further increased, say beyond 78 or 80 per cent., we get again a practically infusible body. But with a paste of this composition the resultant ware is no longer translucent--we pass from the region of porcelain to a true stoneware.