196 THE DYNAMIC STATE OF CHEMICAL COMPOUNDS. 



molecular state which produces the rigidity of solids, is not 

 yet known, yet the molecules are not there at rest, being agi- 

 tated by heat and, probably, intra-molecular movements. The 

 hypothesis of S. Brown here comes in. He holds that the 

 chemical state forms always a counterpart of the astronomical 

 state of the distribution of matter. That in each molecule 

 formed by the combination of separate atoms we have, as it 

 were, a solar system. The atoms are supposed not to be indefi- 

 nitely near each other, as was uniformly assumed, but their 

 " distances may be as great in proportion to the diameters of 

 those particles as, say, the distances of the planets from the 

 sun, in proportion to their diameter and his."* In the molecule 

 the " atoms revolve around each other in the line of the revolu- 

 tion of the centripetal and centrifugal forces, while of two 

 unequal and dissimilar particles (as an oxygen and a hydrogen) 

 the less particle shall be planetary and the other solar." " Each 

 water-particle is a true unit, with its centre neither in the oxy- 

 gen particle nor in the hydrogen, but in the shifting focal point 

 of the forces of both." In commenting on Dalton's reason why 

 carbon cannot combine with more than two atoms of oxygen, 

 viz., that " in the state of CO 2 there are two atoms of oxygen 

 combined with one of carbon, and a third or fourth atom of 

 oxygen, however it may be attracted by the carbon, cannot join 

 it without repelling one or more of the atoms already combined. 

 The attraction of the carbon is able to restrain the mutual re- 

 pulsion of- two atoms of oxygen, but not of three or more." To 

 this S. Brown says, " This lucid conception may be made more 

 lucid still, perhaps, by the counter statement in astronomy 

 that a sun cannot be overloaded with planets." Then, after 

 illustrating this by the constitution of ammonia, he concludes, 

 " It remains to be seen whether there are any data of a purely 

 dynamical sort to determine how many planetary hydrogens 

 there must be in a compound atomic system of ammonia. If 

 there be, or if any can be found, then the atomic theory shall 



* Professor Challis also concludes that the proportion of space occu- 

 pied by the atoms is exceedingly small compared to the ethereal streams 

 and movements surrounding them (" On the Math. Principles of 

 Physics," 1873). 



