170 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



of considerable mathematical ability, developed bis own views 

 of the theory of action at a distance. He regards the material 

 nniverse as "a vast and wonderful mechanism, of which not 

 the least w^onderful thing is its being so constructed that we 

 can understand it." The world, according to Professor Chal- 

 lis, is made up of atoms and ether. The atoms are spheres 

 unalterable in magnitude and endowed with inertia, but with 

 no other property whatever. The ether is a perfect fluid, 

 endued wnth inertia, and exerting a pressure proportionate 

 to its density. It is continuous, and, therefore, does not con- 

 sist of atoms, and fills up all the interstices of the atoms.' 

 The two constituents of the universe, therefore, are atoms, 

 which we can picture in our minds as so many marbles; and 

 the ether, which behaves exactly as air would do, if Boyle's 

 (or Mariotte's) law were strictly accurate, if its temperature 

 were invariable, and if it were destitute of viscositv, and if 

 gravity did not act upon it. Professor Challis sets before him 

 "the task of explaining all actions betw^een bodies or parts of 

 bodies, whether in apj^arent contact or at stellar distances, by 

 the motion of this all-embracing ether, and the pressure 

 thence resulting. The hyj^othesis with which we thus start," 

 says Nature, "is certainly not embarrassed with any indefinite 

 or ill-defined conceptions of the properties of the elements of 

 matter." Without going through the mathematical solutions 

 given by Challis in the work referred to, we may merely in- 

 dicate the nature of the problems that he undertakes to solve. 

 He introduces the Newtonian law of attraction, varying in- 

 versely as the square of the distance, as a consequence of the 

 periodic motion of the particles of ether, but is not able to 

 deduce the numerical value of the influence exerted by 

 the particles of ether upon the atoms of which matter is 

 constituted. Having, liowever, by the vibrations of the 

 etherial particles, set in motion the atoms of matter, lie 

 shows that attractions and repulsions will result. Besides 

 the w'aves of ether, the author contemplates streams, spiral 

 and otherwise, and, through these, accounts for electric, mag- 

 netic, and galvanic phenomena. The work under consider- 

 ation, considering it as a theory explaining the nature of 

 the force of gravitation, is to be compared only witli that 

 put forth by Le Sage, and known as the dynamical theory, 

 the defects of which have, during the past two years, been 



