LAUGEL'S PROBLEMS OF XATUKE AND LIFE. 323 



when we speak of heat as a force, consisting integrally 

 in certain atomic motions of bodies, which force may 

 be pent up for ages in these atomic recesses, yet ever 

 ready for extrication, we are bound to look fairly at 

 the abstract conceptions these things involve, if indeed 

 they can be truly understood in any other way than as 

 simply expressing phenomena. The word Force, with 

 all the adjuncts imposed upon it, still looms before us, 

 as a mysterious symbol, rather than an intelligible 

 reality. 



We have been led to dwell long on this subject from 

 feeling that the conception of Force the very back- 

 bone, we may call it, of physical science has been 

 grievously disjointed by the various and vague use made 

 of the term. Whether any word or phrase could be 

 devised giving more unity to the idea, and to the phe- 

 nomena it embodies, may be doubtful. We do not 

 ourselves venture to suggest one. The radical difficulty 

 lies in the mysteries of nature itself, which we have 

 not sufficiently penetrated to draw this unity from their 

 depths. Such difficulty becomes more manifest as we 

 pursue the subject into other of its ramifications. If we 

 do so here, it is less for the purpose of exposing the 

 deficiencies of our knowledge than to show what science 

 has done, or is yet seeking to do, in the several cases 

 where Force is brought in as the exponent of pheno- 

 mena. 



We pass over mechanical forces, though to these 

 also some of the foregoing remarks will apply. Coming 

 to gravitation, we are on smoother ground as regards 

 the sequence of facts and the phraseology expressing 



Y 2 



