RECORDS 37 



tance would require light about three thousand years to pass 

 over it, while the average distance asunder of the visible stars 

 is considerably less, but still of the same order. Lord Kelvin 

 has shown also in a profound mathematico-physical investiga- 

 tion recently published ^ how we may assign limits to the amount 

 of mass in the visible universe. It appears from this investiga- 

 tion that there are something like a thousand million masses of 

 the magnitude of our sun within that universe. The figures 

 for this amount of mass have little meaning to most of us when 

 expressed in ordinary units. The mass of the earth, for exam- 

 ple, with its 6,000 X lo'"^ metric tons," is a mere trifle, for the 

 sun has about 327,000 times as much mass as the earth. The 

 mass of the sun therefore is the obviously convenient unit in 

 this case ; and we have only to imagine our solar system sur- 

 rounded by a thousand million such suns, each in all probability 

 attended by a group of planets, to get a sufficiently clear idea 

 of the quantity of mass within visual range of our relatively 

 insignificant terrestrial abode. And the time scale for the 

 varied events which take place in the interaction of these mil- 

 lions of suns is not less imposing when expressed in familiar 

 terms. A million years is the smallest unit suitable for esti- 

 mating the history of a star, although the record of that his- 

 tory is transmitted to us through the interstellar medium by 

 vibrations whose period is so brief as almost to escape detection. 

 Measurements and calculations have thus made known to us 

 a range of phenomena which is limited only by our sense per- 

 ceptions, sharpened and supplemented by the refinements of 

 mathematical analysis. In space and mass relations these phe- 

 nomena exhibit all gradations from the indefinitely small to the 

 indefinitely large ; and in time they point backward to no epoch 

 which may be called a beginning and forward to no epoch 

 which may be called an end. Dealing chiefly with those as- 

 pects of phenomena which possess permanence and continuity, 



•"On Ether and Gravitational Matter through Infinite Space," Philosophical 

 Magazine, August, 1901. "On the Clustering of Gravitational Matter in any Part 

 of the Universe," Nature, Vol. 64, No. 1669. 



2 The metric ton of 1,000 kilograms, or 2,205 pounds, is about the same as our 

 " long ton " of 2,240 pounds. 



