642 THE PRINCIPLES OF SCIENCE. [CKAP. 



plexities with which theory cannot cope. Nevertheless, 

 Whewell, observing that the tides of the German Ocean 

 consist of interfering waves, which arrive partly round the 

 North of Scotland and partly through the British Channel, 

 was enabled to predict that at a point about midway be- 

 tween Brill on the coast of Holland, and Lowestoft no tides 

 would be found to exist. At that point the two waves 

 would be of the same amount, but in opposite phases, so 

 as to neutralise each other. This prediction was verified 

 by a surveying vessel of the British navy. 1 



Prediction in other Sciences. 



Generations, or even centuries, may elapse before man- 

 kind are in possession of a mathematical theory of the con- 

 stitution of matter as complete as the theory of gravitation. 

 Nevertheless, mathematical physicists have in recent years 

 acquired a hold of some of the relations of the physical 

 forces, and the proof is found in anticipations of curious 

 phenomena which had never been observed. Professor 

 James Thomson deduced from Oarnot's theory of heat that 

 the application of pressure would lower the melting-point 

 of ice. He even ventured to assign the amount of this 

 effect, and his statement was afterwards verified by Sir W. 

 Thomson. 2 " In this very remarkable speculation, an en- 

 tirely novel physical phenomenon was predicted, in antici- 

 pation of any direct experiments on the subject ; and 

 the actual observation of the phenomenon was pointed out 

 as a highly interesting object for experimental research." 

 Just as liquids which expand in solidifying will have the 

 temperature of solidification lowered by pressure, so liquids 

 which contract in solidifying will exhibit the reverse effect. 

 They will be assisted in solidifying, as it were, by pressure, 

 so as to become solid at a higher temperature, as the pres- 

 sure is greater. This latter result was verified by Bunsen 

 and Hopkins, in the case of paraffin, spermaceti, wax, and 

 stearin. The effect upon water has more recently been 

 carried to such an extent by Mousson, that under the vast 



1 Whewell's History of tJie Inductive Sciences, vol. ii. p. 471. 

 Herschel's Physical Geography, 77. 



* Maxwell's Theory of Heat, p. 174. Philosophical Magazine, 

 August 1850. Third Series, vol. rtxvii. p. 123. 



