68 ANNUAL OF SCIENTIFIC DISCOVERY. 



USE OF PARACHUTES IN MINES. 



IT is well known that vertical ladders for descending into deep 

 mines are very fatiguing, so that the miners prefer to trust themselves 

 to baskets suspended by ropes, and in many cases the baskets are the 

 only means provided for descending and ascending. But accidents 

 frequently occur from the breaking of the ropes, in spite of all the 

 precautions that can be taken to prevent it. The Brussels Herald 

 states that some experiments have lately been made on a large scale 

 in Belgium with a contrivance intended to remedy this evil. The 

 basket or cuffat is so made, that, in case the rope breaks, it imme- 

 diately springs open, forming a sort of parachute, which is held sus- 

 pended in the air by means of the strong current which, it is well 

 known, is always rushing up from mines, owing to the temperature 

 below being higher than that above. The effect of this apparatus 

 was shown before a numerous company, several miners intrusting 

 themselves to the basket, which was so arranged that at a certain 

 point the rope broke ; they were sustained in the air by the open bas- 

 ket, so that the experiments were entirely satisfactory. 



GREAT DAM AT HADLEY FALLS. 



DURING the past year, a dam has been completed across the Con- 

 necticut River at Hadley Falls, 10 miles north of Springfield, Mass., 

 which is believed to be the largest in the United States. It forms a 

 portion of the works of a large manufacturing company, which is in- 

 corporated with a capital of $4,000,000. They own about 1,200 

 acres of land and the entire water-power, which is very great, as the 

 fall of water in the river at that point is about 59 feet. A dam built, 

 as is the present one, of wood, was carried away the day that the 

 gates were first closed, in the fall of 1848, owing, as is supposed, to 

 some peculiarity in the strata of the rock which forms the bed of the 

 river. The present structure is 1,017 feet long, and is an improve- 

 ment upon the old cribbing plan. It is built of solid timbers, 12 inch- 

 es square, laid crosswise, one above another, with a pitch up-stream, 

 and all bolted and pinned together, sunk to the average depth of 4 feet 

 into the solid rock in the bed of the river, and there firmly secured. 

 All the open space between the timbers is filled up with stones for 15 

 feet from the bottom, and a large bed of gravel is laid before the struc- 

 ture, to render it tight and firm. The width of the dam at the base is 

 90 feet, and its height varies with the bed of the river, from 28 to 32 

 feet. The slope from the top to the upper edge of the base is on the 

 angle of 21 degrees. The covering is of plank, 6 inches thick, bolt- 

 ed down to the timbers. The upper part and ridge are double- 

 planked, and the ridge, which is pitched down-stream, is covered 

 with thick boiler-plate, to protect it from the ice. The amount of 

 timber in the dam is about 4,000,000 feet, and the pressure which the 

 dam is required to sustain, when there is but two feet of water on the 

 ridge, is upwards of 44,000 tons. 



The abutments and bulkhead, which together occupy about 200 



