306 The N.Z. Journal of Science and Technology. [July 
general four other faces were also exposed, on which, of course, no glazing 
existed. 
After immersion under pressure for sixty-nine hours the specimens 
were taken out, washed, and weighed, and then cut across somewhere about 
in the middle of the specimen, and the faces exposed by this cut are shown 
in the accompanying photograph. 
The increase in weight indicated that the penetration had been marked, 
but the photograph brings out some interesting and important points. 
Unfortunately, the fuchsin colouring photographs very badly, and so the 
