500 INTERNATIONAL SCIENCE. 



While in the case of scientific units complete agreement is abso- 

 lutely essential, uniformity is desirable in other cases. There are 

 matters of nomenclature in which confusion has arisen purely from 

 want of general agreement. Thus the recent great improvement in 

 the optical })Ower of telescopes has led to the discovery of many 

 details on the surface of the moon. Small craters or other distinctive 

 features named by one observer Avere not correctly identified by 

 another, so that at the present time the same name is ai)plied to quite 

 different things by different observers. It is quite clear that an inter- 

 national agreement in lunar nomenclature is called for. 



There are other deficiencies of uniformity which perhaps appear 

 trivial, but which yet lead to the waste of a good deal of time. Such, 

 for instance, is the position of the index in scientific books. The 

 index is placed sometimes at the beginning, sometimes at the end, and 

 sometimes neither at the beginning nor at the end. Some books have 

 no index, some have two — one for the subject-matter and one for 

 names of authors. The loss of time which arises from one's ignorance 

 as to where to look for the index can not be estimated simply b}^ what 

 is spent on the search, but must include the time necessary to regain 

 the placidity of thought which is essential to scientific work. 



We must now turn to the more serious aspect of those international 

 associations which aim directly at an advance of knowledge. Mathe- 

 maticians have drawn interesting conclusions from the contempla- 

 tion of ideal beings who are confined to live on the surface and have 

 no knowledge of anything that goes on outside the surface. Our 

 Euclidean geometry would bo unknown to them, and spiritualistic 

 tricks could be performed by anyone possessing even to a minute 

 extent the power of controlling a third dimension. It is, I think, 

 worth while investigating the extent of the direct knowledge of a 

 third dimension, which makes us so infinitely superior to the two- 

 dimensional beings. We are able no doubt, through our eyes, to pene- 

 trate the depths of space, but we should be unable to interpret the 

 impressions of our sight if we had not some tangible knowledge of 

 three dimensions and had not learned to bring the sense of sight and 

 the sense of touch into harmony. But our sense of touch is confined 

 to a very small distance from the ground on which w^e stand, and, 

 independently of artificial means of raising ourselves above the sur- 

 face of the earth, a layer 6 or 7 feet thick represents the extent of our 

 three-dimensional knowledge. Compared with the radius of the 

 earth the thickness of such a layer is small enough, for it avouIcI rep- 

 resent only the thickness of a sheet of paper on a sphere having a 

 radius of 250 meters. Compared with the solar system, and even 

 more so with stellar distance, a thickness of 7 feet seems infinitesimal ; 

 yet the infinitesimal is essentially different from the zero, and even 

 were our bodies much smaller than they are we should continue to 



