In the second case (39) are the Molybdates and molybdic acid; the Chromates, including red lead ore from the Siberian gold mines of Beresof; chromate of lead and copper, and crome iron from Var, in France;--the Borates, including borates of magnesia, and borate of soda, or borax. In the third case (40) are some remarkable varieties of silicates, which contain borates from Norway and other countries; and in the fourth case (41) are the first in order, of the carbonates, including carbonates of soda, the beautiful crystals of carbonate of baryta, carbonate of strontia and aragonites, from Aragon, Hungary, Bohemia, and Vesuvius; and in the next case (42) are deposited further varieties of aragonite, and some remarkable varieties of calcite, or carbonate of lime. The next three cases (43-45) are chiefly devoted to the various crystallisations of calcite, including that generally known as the Fontainbleau crystallised sandstone, and the stalactic and fibrous varieties from Africa, Sweden, and Cumberland; while the two cases marked 45 A and B are covered with polished samples, known to people generally as marbles, including the beautiful fire marble. The forty-sixth case is also covered with calcites, including the reastone, the limestone incrusted upon a human skull, found in the Tiber at Rome. In the 47th case are varieties of carbonate of magnesia, and magnesian limestone, including a remarkable one from Massachusetts. Some marble tables are also in this room, placed here to exhibit the beauties of various calcites. The table of Serpentine is here: also the table inlaid with porphyries; one with a series of bivalve shells (25); and in the centre of the room is the stalagmitic table, from the Blythe lead mine, Derbyshire, with black marble legs from Bakewell, given to the trustees of the Museum by the Duke of Rutland. Before leaving this room the visitor should not fail to notice the Maidstone Iguanodon deposited in a bed of sandstone, and placed beneath the central north window of the room. The bones are disjointed, but the general form of the reptile may be more perfectly seen here than in any other fossil remains of the iguanodon. Having noticed this fossil, and remarked the classed groups of gigantic dark fossil bones, which cover the southern wall, the fossil turtles from Sussex and other parts, and the great fossil thigh bones of reptiles that have passed long since from the face of the earth, the visitor should once more advance into the fourth room of the gallery. In this room the wall cases are devoted to FOSSIL ANIMALS.