506 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



constant force of gravity and the vertical component of the 

 wave motion. For example, supposing the force of gravity 

 for three seconds one fifth greater, and for the next three sec- 

 onds one fifth less than its natural intensity, and suppose that 

 we have a weight of five tons suspended by a spring, so that 

 the spring will continue to exert a uniform upward force of 

 five tons, no matter how far the weight moves up and down, 

 it is clear that during the three seconds in which gravity is 

 one fifth more than its normal intensity the five tons' weight 

 will virtually weigh six tons, and will thus exceed the up- 

 ward force with the spring by a downward force of one ton. 

 Similarly, when the force of gravity is one fifth less, the 

 weight will only weigh four tons, and the spring will then 

 exert an unbalanced or upward force of one ton. If now, 

 during the supposed interval, the weight moves downward 

 through one foot, and during the minus interval it moves up- 

 ward one foot, it is clear that during each of these intervals 

 it will exert a force of one ton moving through one foot : 

 that is, one foot ton. But if, instead of one foot, it moves 

 through ten feet, it will exert ten times the power; that is, 

 ten foot tons. Mr. Tower finds, from experiments with the 

 model, that the best arrangement is by putting the weight 

 on the end of a revolving arm, whereby a centrifugal force, 

 with the wave motion, may be utilized as well as the rising 

 and falling motion. If the weighted arm is compelled to 

 assume successive angular positions, so that it is always at 

 right angles with the force, it is evident that the force will 

 be continually acting to cause the arm to rotate. When the 

 vessel is descending, the weight is performing the upper half 

 of its revolution, and is consequently exerting an upward 

 centrifugal force ; and when the vessel is ascending, the cen- 

 trifugal force is pushing down and resisting the vessel's as- 

 cent. 12 A, XL, 410. 



LIQUID CARBONIC ACID AS A MOTIVE POWER. 



Mr. Walter N". Hill, chemist to the United States Naval 

 Torpedo Station at Newport, has written a paper for the 

 Naval Bureau of Ordnance on the experiments and practice, 

 at the Torpedo Station, with liquid carbonic acid as a motor 

 for certain varieties of movable torpedoes. 



The use of compressed air has been for some time familiar 



