33b THE POPULAR SCIENCE MONTHLY. 



in the space of a few minutes." The nature of this eruptive force is 

 not understood. If caused, as we may reasonably assume, by chemical 

 combinations among the solar elements, it was probably in active 

 operation long before the sun had contracted to its present dimen- 

 sions. 



2. With an initial velocity of projection equal to 380 miles per 

 second, the matter thrown off from the sun would' be carried beyond 

 the limits of the solar system, never to return. With velocities some- 

 what less, it would be transported to distances corresponding to those 

 of the aphelia of the periodic comets. 



3. In the explosion witnessed by Prof. Young on the 7th of 

 September, 1871, 1 the mean velocity between the altitudes of 100,000 

 and 200,000 miles was 166 miles per second. This indicates a velocity 

 of about 200 miles per second at the lower elevation, and hence a con- 

 siderably greater initial velocity. An equal force when the sun had 

 but little more than twice its present diameter would have been suffi- 

 cient to carry the projected matter beyond the orbit of Neptune. 



4. This eruptive force, whatever be its nature, is probably common 

 to the sun and the so-called fixed stars. If so, the dispersed fragments 

 of ejected matter ought to be found in the spaces intervening between 

 sidereal systems. Accordingly, the phenomena of comets and meteors 

 have demonstrated the existence, in immense numbers, of extremely 

 small cosmical bodies in the portions of space through which the solar 

 system is moving. The origin of such masses, their collocations in 

 groups, and their various physical characteristics, would seem to be 

 satisfactorily accounted for by the theory under consideration. 



5. According to Mr. Sorby, 2 the microscopic structure of the aero- 

 lites he has examined points evidently to the fact that they have been 

 at one time in a state of fusion from intense heat a fact in striking 

 harmony with this theory of their origin. 



6. The velocity with which some meteoric bodies have entered the 

 atmosphere has been greater than that which would have been ac- 

 quired by simply falling toward the sun from any distance, however 

 great. On the theory of their sidereal origin, this excess of velocity 

 has been dependent on the primitive force of expulsion. 



7. A striking argument in favor of this theory may be derived 

 from the researches of the late Prof. Graham, considered in con- 

 nection with those of Dr. Huggins and other eminent spectroscopists. 

 Prof. Graham found large quantities of hydrogen confined in the 

 pores or cavities of certain meteoric masses. Now, the spectroscope 

 has shown that the sun's rose-colored prominences consist of immense 

 volumes of incandescent hydrogen; that the same element exists in 

 great abundance in many of the fixed stars, and even in certain nebu- 

 lae ; and that the star in the Northern Crown, whose sudden outburst 



1 Boston Journal of Chemistry, November, 1871. 

 8 Proceedings of Royal Society, January, 1864. 



