176 Sir John Herschel on this subject. CHAP. 



by a steam-engine of very small power in proportion 

 to the engines that propel the ship, which small 

 engine is under the engineer's direct control. And 

 similarly, the rudder is not worked directly by the 

 steersman, but by a small steam-engine which the 

 steersman controls. And to mention a still more 

 striking instance of a very great force controlled by 

 a very small one ; a touch on an electric button by 

 a child of ten years old exploded the vast mines of 

 dynamite which in a moment rent the rocks of Hell- 

 gate asunder, and opened a new channel into the 

 harbour of New York for the largest ships in the 

 world. Are not these significant symbols of the 

 control of Will over the muscular forces 1 



But in reply to this, it is urged that the analogy 

 fails unless it were possible for the will of the engineer 

 to control the engines without the exertion of muscular 

 power at all ; and however this may be diminished by 

 refinement of mechanism, it can never be reduced 

 absolutely to nothing. 



Sir John Herschel saw the difficulty, and appears 

 to have concluded that the will can and does produce 

 energy, though in quantity so minute as to be incap- 

 able of experimental proof. This is cutting the 

 knot rather than untying it. I quote his words : 

 " The actual farce necessary to be originated to give rise 

 to the utmost imaginable exertion of animal power 

 in any case, may be no greater than is required to 

 remove a single material molecule from its place 

 through a space inconceivably minute; no more 



