262 THE PRINCIPLES OF SCIENCE. 



respect by the most marked qualities. Of all known 

 substances water has the highest specific heat, being thus 

 peculiarly fitted for the purpose of warming and cooling, 

 to which it is often put. It rises by capillary attraction 

 to a height more than twice that of any other liquid. In 

 the state of ice it is nearly twice as dilatable by heat as 

 any other known solid substance 11 . In proportion to its 

 density it has a far higher surface tension than any other 

 substance, being in fact surpassed in absolute tension only 

 by mercury, and it would not be difficult to extend con- 

 siderably the list of its remarkable and useful properties. 



Under extreme instances we may include cases of re- 

 markably low powers or qualities, equally with those of 

 the opposite extreme. Such cases seem to correspond to 

 what Bacon calls Clandestine Instances, which exhibit a 

 given nature in the least intensity, and as it were in a 

 rudimentary state . They may often be important, he 

 thinks, as allowing the detection of the cause of the pro- 

 perty by difference. I may add that in some cases they 

 may be of use in experiments. Thus hydrogen is at once 

 the least dense of all known substances, and has the least 

 atomic weight. Liquefied nitrous oxide has the lowest 

 refractive index of all known fluids P. The compounds of 

 strontium have the lowest dispersive powers on light. It 

 will be obvious that a property of very low degree may 

 prove as curious and valuable a phenomenon as a property 

 of very high degree. 



The Detection of Continuity. 



We should always bear in mind that phenomena which 

 are in reality of a closely similar or even identical nature, 



n ' Philosophical Magazine,' 4th Series, January 1870, vol. xxxix. p. 2. 

 'Novum Organum,' bk. II. Aphorism 25. 



P Faraday's ' Experimental Researches in Chemistry and Physics,' 

 P- 93- 



