Prof. Ridgway, of Pennsylvania, has lately made a re-examination of the Mansfield coal mine, and says that the coal has improved 20 per cent, in quality by descending 80 feet deeper. The Hoosick Tunnelling Machine has proved a failure. It cut into the rock, the account says, a distance of 25 linear feet, when the machine was pretty well used up. It progress was from 24 to 18 inches per hour, and the core which it drilled, had to be blasted out, which destroyed the work as far as it was performed, as it brought down the roof and all, to the amount of 300 tons of rock ai.d earth.