40 THE SEVEN FOLLIES OF SCIENCE 



Dr. Hooper, in his "Rational Recreations," has described 

 a method of driving a clock by the motion of the tides, and 

 it would not be difficult to contrive a very simple arrange- 

 ment which would obtain from that source much more 

 power than is required for that purpose. Indeed the prob- 

 ability is that many persons now living will see the time 

 when all our railroads, factories, and lighting plants will be 

 operated by the tides of the ocean. It is only a question 

 of return for capital, and it is well known that that has 

 been falling steadily for years. When the interest on in- 

 vestments falls to a point sufficiently low, the tides will be 

 harnessed and the greater part of the heat, light, and power 

 that we require will be obtained from the immense amount 

 of energy that now goes to waste along our coasts. 



Another contrivance by which a seemingly perpetual 

 motion may be obtained is the dry pile or column of De Luc. 

 The pile consists of a series of disks of gilt and silvered 

 paper placed back to back and alternating, all the gilt sides 

 facing one way and all the silver sides the other. The so- 

 called gilding is really Dutch metal or copper, and the sil- 

 ver is tin or zinc, so that the two actually form a voltaic 

 couple. Sometimes the paper is slightly moistened with 

 a weak solution of molasses to insure a certain degree of 

 dampness ; this increases the action, for if the paper be 

 artificially dried and kept in a perfectly dry atmosphere, 

 the apparatus will not work. A pair of these piles, each 

 containing two or three thousand disks the size of a quarter 

 of a dollar, may be arranged side by side, vertically, and 

 two or three inches apart. At the lower ends they are 

 connected by a brass plate, and the upper ends are 

 each surmounted by a small metal bell and between these 

 bells a gilt ball, suspended by a silk thread, keeps vibrating 



