xii TOWARDS INFINITY 325 



evidence of the spectroscope has shown that a star 

 which passed for a single body until a few years ago 

 has really a partner which insists upon making its 

 presence known. 



The North Star Polaris also shows by its move- 

 ments that it is under the influence of one or more bodies 

 near it. In a period of about four days the star is found 

 to swing back and forth, doubtless as the result of 

 movement in an orbit. Moreover, there are indications 

 that Polaris and its satellite are in revolution together 

 around a third body, so that the system must be regarded 

 as a triple one. The movements of the moon and earth 

 with reference to the sun provides us with a similar 

 case, though on a much smaller scale ; for the moon 

 revolves around our globe once a month, while the earth 

 itself is traversing its annual path around the sun. 



The few cases of dark stars already mentioned repre- 

 sent only the first fruits of the inquiry into the invisible 

 worlds in space. It is estimated that one star in every 

 three or four thus far investigated has near it a partner 

 which can never be seen. New methods of inquiry may 

 reveal many bodies beyond the power of the telescope 

 to show to human eyes, but even as the evidence stands 

 at present, we are assured of the existence of a vast 

 universe of invisible stars. The astronomy of the future 

 will be concerned as much with the study of these dark 

 masses as with those from which luminous radiations 

 are received. 



The spectroscope has demonstrated the reality of dark 

 stars, but there are other means by which evidence of 

 the existence of invisible matter in space has been 

 obtained. The telescope and photographic camera have 

 shown that what seem to be blank regions of the sky in 

 many cases are crowded with sparkling points and realms 



