THE PROGRESS OF PHYSICS. 133 



round and presenting a new face to us? We can 

 do little more than guess. We cannot get round 

 to the other side of the pattern, and our minutest 

 watching will not tell us all the working of the 

 loom." 11 But since we cannot rest with discon- 

 tinuous descriptions, we construct a hypothetical 

 system as to the constitution of matter and the 

 relation of energy to it, a system in line with what 

 we do know of visible motions and accelerations, 

 a system to which we will naturally hold until a 

 more complete knowledge should suggest some im- 

 provement of it, or, it might be, demand its rejection. 

 SUMMABY. In the main the problem of the phys- 

 icist is to describe and formulate the likenesses of 

 motion which are observed in our outlook upon 

 nature. 



THE NEWTONIAN FOUNDATION. 



At the beginning of the nineteenth century, chem- 

 istry was just steadying itself on the foothold afforded 

 by the doctrine of the indestructibility of matter, but 

 Physics had been on sure ground since the publication 

 of Xewton's Principia (1687). It seems necessary 

 to admit that the value of the Xewtonian foundation 

 was not fully appreciated in the eighteenth century, 

 and that many workers left it and built short-lived in- 

 dependent structures, but for the nineteenth century 

 it does not seem too much to say that all stable prog- 

 ress in Physics has been dominated by Newton's con- 

 clusions. " In fact the Newtonian philosophy can be 

 said to have governed at least one entire section of the 

 scientific research of the first half of this period : only 

 in the second half of the period have we succeeded in 



* Poynting, Address, Section A, Rep. Brit. Ass. for 1899, 

 p. 618. 



