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 dimensions.
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 somewhat 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 considerably greater initial velocity. An equal force when the sun had but little more than twice its present diameter would have been sufficient 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 aërolites 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 acquired 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 connection 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 nebulae; and that the star in the Northern Crown, whose sudden outburst
