296 KANSAS CITY REVIEW OF SCIENCE. 



admitting the water to them from the pool above head of the lock, through the side 

 wall, when the pressure of the water pressed them up. They were prevented 

 from going too far by shoulders in the recesses. The gates then came within lo 

 or 15 degrees of being at right angles to each other, the under side of the up- 

 stream gate resting on the upstream edge of the downstream gate. They could 

 be held in any position, so as to hold back the water entirely, or let it run over 

 with more or less volume, as required. The arks containing the coal were com- 

 monly shot through over the partly raised gates as over so many dams. 



Such locks, copied from those on the Lehigh, are now in use on the Ottawa, 

 at the Canadian capital. Many of us at our last convention were shot through 

 them on rafts. 



It is well worth inquiry whether these bear-trap gates would not be the best 

 possible, and possibly the cheapest, for letting the water rapidly out of a reservoir 

 for scouring purposes. A full stream could be set running in a few seconds, and 

 the flow could be regulated with perfect ease, and stopped at any moment. 



In many rivers it is desirable to dam the stream back at low water, and let 

 it run freely at high water In Belgium, on the Meuse, they use needle dams 

 for this purpose. Another probably better adjustable dam is in use in France. 

 The bear-trap gates, with proper appliances, on a solid platform at the bo.tom of 

 a river, would enable a man on shore to raise a dam across that river, or if raised, 

 to lower it to the bottom, in a few minutes. 



I have used this contrivance for a fish sluice in a permanent dam, by which 

 the water ran freely through the sluices when necessary, and at other times was 

 retained at full height. 



The coal, on the descending navigation of the Lehigh, was sent to market in 

 arks consisting of six boxes, sixteen feet square and twenty inches deep, coupled 

 by hinges, the whole carrying about 100 tons. 



^ ■:^ -^ i^ ^ •:^ 



About fifty years ago. Professor Henry made a series of brilliant discoveries 

 in electro magnetism, one of which was, that by means of a current through a 

 wire, a signal could be made and information given (by ringing a bell, for ex- 

 ample), a long distance off. Years afterward, Steinheil, Morse, Wheatstone and 

 others, applied Henry's discovery to the actual conveyance of information ; 

 Morse's apparatus, as it seems to us Americans, being by far the best. The wonder 

 to us now is, why Henry himself did not apply his discovery, and why others did 

 not sooner do so. The answer is found in a very important phase of human 

 mind. The habit of mind into which the scientist is liable, perhaps likely, to 

 fall, is to look at scientific result as his ultimate end. Such result arrived at, the 

 same habit of mind is to use it only to attain further scientific result. Hence, 

 men of science so rarely are benefited pecuniarily by their own researches. 

 Hence, also, it frequently happens that engineers who have kept at their studies 

 without practice till too late in life, are so often less successful than those of far 

 less science, and, perhaps, less intellect, but who have been early trained to ap- 

 ply to practical use what science they have. 



