82 Mr. H. Wilde's Experimental Researches 



bottom or side of a vessel with a velocity which a body would 

 acquire in falling freely from the surface, is equal to the weight 

 of a column of water of which the base is equal to the section 

 of the contracted vein, and about twice the height of the co- 

 lumn which produces the flowing pressure, — the static force 

 of reaction being thus double that which, without experiment, 

 had been predicted*. An instance in which the quantity of 

 dynamic force is increased paradoxically may be seen in that 

 curious and useful piece of apparatus the injector, by means of 

 which a boiler containing steam of high pressure is able to feed 

 itself with water through a hole in its shell, though this hole is 

 open to the atmosphere, or the steam from a low-pressure 

 boiler is enabled to drive the feed-water through a hole (also 

 open to the atmosphere) into a high-pressure boiler. Although, 

 when rightly interpreted, these examples of paradox, as well as 

 many others of a similar character, are in strict accordance with 

 the principle of conservation, yet they are at the same time 

 contrary to the inferences which are generally drawn from 

 analogical reasonings, and to some of those maxims of science 

 w T hich are framed for the instruction of the unlearned. As the 

 examples cited are only adduced for the purpose of illustrating 

 some analogous phenomena observed in connexion with certain 

 combinations of static and dynamic force in molecular mechanics 

 which form the subject of the present research, it is not my 

 intention to enter into the rationale of either of them, but 

 to direct attention to some new and paradoxical phenomena 

 arising out of Faraday's important discovery of magneto-electric 

 induction, the close consideration of which has resulted in the 

 discovery of a means of producing dynamic electricity in quan- 

 tities unattainable by any apparatus hitherto constructed. 



3. If round a piece of iron forming the armature of a per- 

 manent magnet a quantity of insulated wire be wound at right 

 angles to the line which joins the poles of the magnet, and if 

 the free ends of the wire be connected together directly, or 

 indirectly by the interposition of some conductor, a momentary 

 wave of electricity, as is well known, is generated in the wire 

 every time the armature is suddenly removed from the magnet, 

 or suddenly approaches it ; and the wave of electricity generated 

 by the removal of the armature moves in the opposite direction to 

 that generated by the approach of the armature. With a descrip- 

 tion of this simple experiment, Faraday announced (in 1831) the 

 discovery of magneto-electricity f, which was found to possess 

 all the distinguishing characteristics of electricity derived from 

 any other source. 



* Pi^incipia, 1st Edition, Book 2. Prop. 3/. 

 f Philosophical Transactions, 1832, vol. cxxii. 



