THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art XXVII. — Generalised Relativity and Gravitation; 

 by E. Woolard. 



The following sketch is decidedly non-mathematical; 

 consequently, the reader must take for granted many of 

 the statements ; in this respect, the paper may be found 

 unsatisfactory, but it may be taken as a fair summary of 

 the present state of the more important aspects of the 

 theory of relativity. We are all put at a disadvantage 

 regarding recent progress in German scientific investi- 

 gations because of the impossibility of obtaining German 

 periodical and other literature. 



I. The "Older" Relativity. 



1. Man, in his study of natural phenomena, is forced 

 to devise some means of describing these phenomena; 

 this he does by creating artificial frames of reference to 

 which the position of points, and the equations express- 

 ing his observations and conclusions, may be referred. 

 We are all familiar with Cartesian rectangular coordi- 

 nates in space, and the transformations by which 

 expressions referred to one set of axes may be changed 

 to refer to other sets of axes, rectangular or oblique, 

 which have been rotated or translated with respect to the 

 original set; evidently there is an infinite number of 

 possible S3^stems of reference. It is perfectly clear that 

 natural phenomena themselves are entirely independent 

 of the reference svstems ; no matter what system of 

 coordinates is used to describe it, a phenomenon itself 



Am. Jour. Sci. — Fourth Series, Vol. XLV, No. 270. — June, 1918. 

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