A system of apparatus, devised by M. Chandron and de signed for sinking the shafts in coal mines, is exhibited in Machinery Hall. 'fhe machines are of colossal size and form, the most prominent feature of the vicinity. There is a tre pan weighing lIi tuns, which is made of forged iron, and fit ted with cutters secured by taper keys, so as to make a cut six feet long. The trepan is raised by steam power to a hight of three feet, and dropped. It is turned at each ele vation so that a circle, six

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... eet in diameter, is cut. The ad vance in soft sandstone is said to be three feet per day. The trepan being withdrawn, a massive iron bucket is fitted into the hole to remove the debris. After the first tool has pene trated about 30 feet, a second trepan, much heavier than the first and having a central guide working in the opening made by the first, is used, and, in the stone above mentioned,