On examining the interior of the pipes, I have invariably found the surface to be more or less decomposed. For about half an inch—sometimes less and sometimes more—the texture and hardness of the limestone is completely changed—so much so that it is possible to scrape it away with the finger-nail. This is the case with all the beds, no matter how they may differ in texture and general character, though some seem more affected than others. This alteration is best seen in those strata that are crystalline. In one part of the quarry is a bed of which the limestone is hard and dolomitic, and also finely laminated, there being more than a dozen laminæ to the inch; this is its normal character, but where it is penetrated by a pipe it looses its hardness, and becomes dull and earthy; the laminæ also, which in the unaltered portion of the pipe are firmly coherent and difficult to separate, are here easily split open, the surfaces of their planes being highly decomposed; the colour, too, of the decomposed portion is somewhat changed, being of a light yellow, while tho limestone of the bed generally is of a brown or grey hue, and so soft has it become where it forms the surface of a pipe that it crumbles to pieces on being touched, and for half an inch in it can be cut with a pocket-knife.