L. A little of everything there's always flint and clay, and magnesia in it, and the black is iron, according to its fancy, and there's boracic acid if you know what that is and if you don't, I cannot tell you today, and it doesn't signify and there's potash, and soda, and, on the whole, the chemistry of it is more like a mediaeval doctor's prescription, than the making of a respectable mineral but it may, perhaps, be owing to the strange complexity of its make, that it has a notable habit which makes it, to me one of the most interesting of minerals. You see these two crystals are broken right across, in many places, just as if they had been shafts of black marble fallen from a ruinous temple, and here they lie, imbedded in white quartz, fragment succeeding fragment keeping the line of the original crystal, while the quartz fills up the intervening spaces Now tourmaline has a trick of doing this, more than any other mineral I know here is another bit which I picked up on the glacier of Macugnaga; it is broken, like a pillar built of very flat broad stones, into about thirty joints, and all these are heaved and warped away from each other sideways, almost into a line of steps, and then all is tilled up with quartz paste. And here, lastly is a green Indian piece, in which the pillar is first disjointed, and then wrung round into the shape of an S. MARY. How CAN this have been done? L. There are a thousand ways in which it may have been done, the difficulty is not to account for the doing of it, but for the showing of it in some crystals and not in others You never by any chance get a quartz crystal broken or twisted in this way. If it break or twist at all which it does sometimes, like the spire of Dijon, it is by its own will or fault, it never seems to have been passively crushed But, for the forces which cause this passive ruin of the tourmaline,--here is a stone which will show you multitudes of them in operation at once It is known as "biecciated agate," beautiful, as you see, and highly valued as a pebble yet, so far as I can read or hear no one has ever looked at it with the least attention At the first glance, you see it is made of very fine red striped agates, which have been broken into small pieces, and fastened together again by paste also of agate There would be nothing wonderful in this, if this were all. It is well known that by the movements of strata, portions of rock are often shattered to pieces:--well known also that agate is a deposit of flint by water under certain conditions of heat and pressure: there is, therefore, nothing wonderful in an agate's being broken; and nothing wonderful in its being mended with the solution out of which it was itself originally congealed. And with this explanation, most people, looking at a brecciated agate, or brecciated anything, seem to be satisfied. I was so myself, for twenty years; but, lately happening to stay for some time at the