670 HENEY A. EOWLAND 



together in its interest, to discuss its problems, to criticise each other's 

 work and, best of all, to provide means by which the better portion of 

 it may be made known to the world. Furthermore, let us encourage 

 discrimination in our thoughts and work. Let us recognize the eras 

 when great thoughts have been introduced into our subject and let us 

 honor the great men who introduced and proved them correct. Let us 

 forever reject such foolish ideas as the equality of mankind and care- 

 fully give the greater credit to the greater man. So, in choosing the 

 subjects for our investigation, let us, if possible, work upon those sub- 

 jects which will finally give us an advanced knowledge of some great 

 subject. I am aware that we cannot always do this: our ideas will often 

 flow in side channels: but, with the great problems of the universe 

 before us, we may some time be able to do our share toward the greater 

 end. 



What is matter; what is gravitation; what is ether and the radiation 

 through it; what is electricity and magnetism; how are these connected 

 together and what is their relation to heat? These are the greater 

 problems of the universe. But many infinitely smaller problems we 

 must attack and solve before we can even guess at the solution of the 

 greater ones. 



In our attitude toward these greater problems how do we stand and 

 what is the foundation of our knowledge? 



Newton and the great array of astronomers who have succeeded him 

 have proved that, within planetary distances, matter attracts all others 

 with a force varying inversely as the square of the distance. But what 

 sort of proof have we of this law? It is derived from astronomical 

 observations on the planetary orbits. It agrees very well within these 

 immense spaces; but where is the evidence that the law holds for smaller 

 distances? We measure the lunar distance and the size of the earth 

 and compare the force at that distance with the force of gravitation on 

 the earth's surface. But to do this we must compare the matter in the 

 earth with that in the sun. This we can only do by assuming the law 

 to be proved. Again, in descending from the earth's gravitation to that 

 of two small bodies, as in the Cavendish experiment, we assume the law 

 to hold and deduce the mass of the earth in terms of our unit of mass. 

 Hence, when we say that the mass of the earth is 5 times that of an 

 equal volume of water we assume the law of gravitation to be that of 

 Newton. Thus a proof of the law from planetary down to terrestrial 

 distances is physically impossible. 



Again, that portion of the law which says that gravitational attrac- 



