102 TWO NEW WORLDS 



the existence of remote worlds. Besides radiation, 

 we have gravitation, electrostatic force, electro- 

 dynamic ("magnetic") force, and magnetic induc- 

 tion. All these may yet be used to explore the 

 supra-world; but in these infantile days of cosmic 

 electricity, we must perforce be content with reason- 

 ing based upon Newton's law of gravitation. 



Lord Kelvin 1 has made an interesting essay in 

 this direction. Assuming the farthest star to have 

 a parallax of 0*001 of a second, which would imply 

 a distance of 3 x 10 21 cm., and that a sphere of that 

 radius surrounding our stellar system contains 100 

 million stars of about the same average mass as 

 the sun, he shows that the mean force of gravita- 

 tional attraction over the surface of that sphere 

 is l'37xlO~ n times that of gravity at the earth's 

 surface. It follows that a body falling into this 

 sphere from infinite outer space would have a 

 speed of some 11 km. (seven miles) per second 

 just about double the planetary velocity of 

 Neptune. 



Meteoric speeds go up to 40 km. per second; 

 but their speed is acquired under the attraction 

 and in the proximity of the sun. The solar system 

 is, according to Campbell, moving with a velocity 

 of 19*89 km. per second towards a point in R.A. 

 277 30' and Dec. 19 58' N. The proper motions 

 of stars show an average velocity of 21 miles per 



1 Philosophical Magazine, August 1901. 



