the increase and obliteration of waves formed on the surface of water." The apparent contradictions in chemistry are, indeed, best exhibited in the lecture-room, where they may be rendered visible and tangible, and brought home to the general comprehension. The Professor of Analytical Chemistry, J.H. Pepper, who demonstrates these things in the Royal Polytechnic Institution, is an expert manipulator in such mysteries; and, taking a leaf out of his own magic-book, we shall conjure him up before us, standing behind his own laboratory, surrounded with all the implements of his art. At our recent visit to this exhibition we witnessed him perform, with much address, the following experiments: He placed before us a pair of tall glass vessels, each filled, apparently, with water; he then took two hen's eggs, one of these he dropped into one of the glass vessels, and, as might have been expected, it immediately sank to the bottom. He then took the other egg, and dropped it into the other vessel of water, but, instead of sinking as the other had done, it descended only half way, and there remained suspended in the midst of the transparent fluid. This, indeed, looked like magic--one of Houdin's sleight-of-hand performances--for what could interrupt its progress? The water surrounding it appeared as pure below as around and above the egg, yet there it still hung like Mahomet's coffin, between heaven and earth, contrary to all the well-established laws of gravity. The problem, however, was easily solved. Our modern Cagliostro had dissolved in one half of the water in this vessel as much common salt as it would take up, whereby the density of the fluid was so much augmented that it opposed a resistance to the descent of the egg after it had passed through the unadulterated water, which he had carefully poured upon the briny solution, the transparency of which, remaining unimpaired, did not for a moment suggest the suspicion of any such impregnation. The good housewife, upon the same principle, uses an egg to test the strength of her brine for pickling.