2 Wilde, Qn Aerial Locomotion. 



3. The notion that relations subsist between gravity, 

 electricity, and magnetism to cause the levitation of 

 bodies, has been seriously as well as humorously sug- 

 gested by several imaginative writers. One of these, 

 M. de la Folie, in his book entitled, Le pJiilosopJie sans 



pretention (1775), has described a levitating machine which 

 derived its ascensional power from frictional electricity 

 generated by means of two large globes of glass. A well 

 designed plate at the head of the work represents the 

 machine at the moment of elevation surrounded by 

 an electrical glory, with the seated figure of a man turning 

 the glass globes and ascending with the machine in the 

 presence of a wondering crowd of spectators. 



4. Dean Swift in his Gulliver had previously (1726) 

 represented Laputa as a levitating island containing a huge 

 loadstone, mounted on a strong axle in such a manner 

 that, when an attractive pole was presented towards the 

 earth the island descended, but when the repellent pole 

 was downwards the island mounted directl}- upwards. 

 The extravagant humour of this description is sobered in 

 the same chapter by the prediction of the two satellites 

 of Mars (discovered by Hall in 1877), with their orbits 

 and times of revolution roughl}- calculated from Kepler's 

 third law. 



5. In the course of a subsequent lecture on Mental 

 Education, delivered before the Prince Consort and the 

 members of the Royal Institution, Faraday had occasion 

 to remark upon the number of abortive theories that must 

 necessarily pass through the minds of the most successful 

 scientific investigators, and be destined to be crushed in 

 silence and secrecy after being put to the test of experi- 

 ment.* This observation accords so closely with my own 



* Observations on Mental Education, 1855. 



