Economy of Machinery and Manufactures. 113 



" Amongst the natural processes, which are perpetually altering the surface of 

 our globe, there are some which it would be desirable to accelerate. The wearing 

 down of the rocks, which impede the rapids of navigable rivers, is one of this class. 

 A very beautiful process for accomplishing this object has been employed in Amer- 

 ica. A boat is placed at the bottom of the rapid, and kept in its position by a long 

 rope, which is firmly fixed on the bank of the river near the top. An axis having 

 a wheel similar to the paddle wheel of a steam-boat fixed at each end of it, is placed 

 across the boat, so that the two wheels and their connecting axis shall revolve rap- 

 idly, being driven by the force of the passing current. Let us now imagine several 

 beams of wood, called stampers, shod with pointed iron, fixed at right angles on the 

 ends of strong levers, projecting beyond the bow of the boat. The levers being at 

 liberty to move up and down, the action of the stream upon the wheels will keep 

 up a perpetual succession of blows. The sharp pointed shoe, striking upon the rock 

 at the bottom, will continually detach small pieces, which the stream will immedi- 

 ately carry away. Thus, by the mere action of the river itself, a constant and most 

 eflFectual system of pounding the rock at its bottom is established. A single work- 

 man, by the aid of a rudder, may direct the boat to any part of the stream ; and when 

 it is necessary to move up the stream, as the channel is cut, he can easily cause the 

 boat to advance by means of a capstan.* When the object of this machinery has 

 been accomplished and the channel is suflSciently deep, a«]ight alteration converts 

 the apparatus to another purpose, almost equally advantageous. The stampers and 

 projecting pieces on the axis are removed, and a barrel of wood or metal surrounding 

 part of the axis, and capable at pleasure of being disconnected from the axis itself, 

 is substituted. The rope, which hitherto fastened the boat, is now fixed to the bar- 

 rel, which being attached to the axis, begins to turn, and winding the rope upon it- 

 self, the boat is gradually drawn up against the stream, and may be employed as a 

 tug-boat for vessels which ascend the rapid. When the tug-boat reaches the sum- 

 mit, the barrel is released from the axis, and friction being applied to moderate its 

 velocity, the boat is allowed to descend." 



" The economy of applying the power of steam to overcome resistances, which it 

 would require a far greater expense to surmount by animal power, is of frequent 

 occurrence in large manufactories. The twisting of the largest cables, the rolling, 

 hammering, and cutting of large masses of iron, the drawing of wires, all require 

 enormous exertions of physical force, continued for considerable periods of time. 

 When the force required is great, and the space through which it is to act is small, 

 other means are adopted. The hydraulic press of Bramah, by the exertion of one 

 man, can produce a pressure of 1500 atmospheres, and with such an instrument a 

 hollow cylinder of wrought iron, three inches thick, has been burst. In rivetting 

 the iron plates to form steam-engine boilers, it is necessary to produce as close a 

 joint as possible. This is accomplished by using the rivets red hot : while they are 

 in that state, the two plates of iron are rivetted together, and the contraction which 

 the rivet undergoes in cooling draws them together, with a force which is only lim- 

 ited by the tenacity of the metal of which the rivet itself is made. 



" It is not alone in the greater operation of the engineer or the manufacturer, that 

 those vast powers, which man has called into action by the agency of steam, are fully 

 developed. Wherever the individual operation, demanding little force for its own 

 performance, is to be multiplied in almost endless repetition, commensurate power 

 is required. It is the same " giant arm, which twists the largest cable, that spins 



* This machine would be very convenient to open passages through the ice for 

 steam boats. 



Vol. XXIVi— No. 1. 15 



