1906.] on International Science. 349 



While in the case of scientific units complete ugreement is absolutely 

 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 

 power 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 were not correctly identified by another, so 

 that at the present time the same name is applied to quite different 

 things by different observers. It is quite clear that an international 

 agreement in lunar nomenclature is called for. 



There are other deficiencies of uniformity Avhich perhaps appear 

 trivial, but w^hich 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 cannot be estimated simply by 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 inter- 

 national associations which aim directly at an advance of knowledge. 

 Mathematicians have drawn interesting conclusions from the con- 

 templation 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 be 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 penetrate 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 we stand, and, independently of 

 artificial means of raising ourselves above the surface of the earth, 

 a layer six or seven 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 would represent only 

 the thickness of a sheet of paper on a sphere having a radius of 250 

 metres. Compared with the solar system, and even more so with stellar 

 distance, a thickness of seven feet seems infinitesimal ; yet the infini- 

 tesimal is essentially different from the zero, and even were our bodies 

 much smaller than they are, we should continue to have the power to 

 interpret three dimensions. These considerations show how important 

 it is for us to increase our knowledge of the earth itself, and to extend 



