1919.] 
New Zealand Institute Science Congress. 
307 
penetration edge was lightly pencilled round and the coloured part cross- 
hatched. ^he two pieces resulting from cutting each specimen are shown in 
general one under the other, except in the case of specimen I, where they 
are side by side. A rotation of the lower piece round its upper edge makes 
it fit the top piece. 
Some features about the penetration may be pointed out. Many of the 
specimens show distinct evidence of a porous core—alb of them, indeed, 
except C, which seems to be porous throughout, and I and J, which show 
no penetration at the section where the cut was made. One or both edges 
of this core are often almost a straight line parallel with the upper or lower 
face of the specimen—parallel, that is to say, to the natural surface of the 
material. This feature is to be seen in specimens A, B, D, E, G, and H, 
but possibly shows itself best in B, where, as in most of the specimens, the 
dye has entered from both of the artificially-formed sides and has got 
nearly right across. It would seem to meet with greater obstruction in 
its passage in from the left side (in the photograph) than from the right 
(of specimen B). The penetration on the right side of this specimen is 
actually about 1 in., and that on the left about J in. The dye, however, 
has not penetrated at all from either the top or the bottom, which were 
the natural shell surfaces. It would seem, therefore, that there is in the 
specimens an abrupt change in the character of the porcelain as one proceeds 
from the natural surfaces inwards, for the colour change is abrupt and not 
gradual (fading away at the edges). It is, indeed, quite as abrupt as the 
photograph shows. 
With regard to specimen C, it will be seen that it absorbed 0-719 of a 
gramme of liquid in a weight of 77-066—a somewhat remarkable perform¬ 
ance, surely. It is not surprising, therefore, that on its being broken the 
dye should show itself over nearly the whole break ; yet even here there is a 
non-porous layer, which shows in the photograph at the bottom edge of 
the top half and at the top edge of the bottom half. It is, however, at 
its widest part only about -3 millimetres wide. The horizontal surfaces of 
this specimen are the natural faces, and both are glazed. 
Conclusions. 
It seems possible to draw the following conclusions from these experi¬ 
ments :— 
(1.) That density and porosity have little or no connection with one 
another. 
. (2.) That porcelain can be made which shows no penetration under 
the pressures which were maintained, and for the times for which 
they were maintained, in these experiments. 
(3.) That porcelain is not always so made. 
(4.) That when it is otherwise a porous layer with abrupt edges very 
often exists in the mass of the substance. 
It is hoped to carry out more experiments with a view to studying 
the matter further. 
My thanks are due to Mr. L. Birks and Mr. G. F. Ferguson, Electrical 
Engineers of the Public Works Department, at whose request the investiga¬ 
tion was carried out, for advice and help; and to Mr. T. E. Kilworth, the 
mechanical assistant in the laboratory, to whose mechanical skill the work 
owes much. 
