36 RECORDS 



When we pass from terrestrial limitations to celestial phe- 

 nomena the field for measurement and calculation is immensely 

 enlarged, though the results attainable are less easy of ready 

 appreciation. The Jovian, the Saturnian and the Martian sub- 

 systems, which have been pretty thoroughly explored by the 

 observer and the computer, present to us the type, apparently, 

 not only of the solar system, but of the galaxy of systems 

 within telescopic view. And the surveys of the heavens now in 

 progress indicate likewise that isolated stars are the exception 

 rather than the rule, and that the visible stars are generally at- 

 tended by one or more satellites, which are probably oftener 

 dark than bright bodies. Visual and photographic measure- 

 ments have, in fact, united in recent years in the demonstration 

 that the number of material bodies in the universe is enormously 

 greater than we have hitherto imagined. Here again, however, 

 as in the case of the geological phenomena just referred to, we 

 must be content to a great extent for the present with a knowl- 

 edge of the order of the quantities measured and calculated. 

 But to be able to state what is the order of the distances which 

 separate the fixed stars from one another, the order of the 

 volume of the visible universe, the order of the quantity of mass 

 in that volume, and the order of the time unit requisite for the 

 expression of the historical succession of celestial events, seems 

 little short of a stupendous contribution to knowledge when one 

 reflects on the obstacles, material and intellectual, that have 

 stood in the way of its attainment. 



The distances asunder of the stars are so great that the hun- 

 dred and ninety odd millions of miles in the diameter of the 

 earth's orbit about the sun make an inconveniently small base 

 line for the measurement of the least of those distances and a 

 hopelessly inadequate one for the measurement of the greatest 

 of them. It would appear more fitting, in fact, to express such 

 distances indirectly in the number of years it takes light moving 

 at the rate of 300,000 kilometers per second to traverse them. 

 Assuming with Lord Kelvin that the visible universe is com- 

 prised within a sphere whose radius is equal to the distance of 

 a star whose parallax is one thousandth of a second, this dis- 



