724 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



One of the latest and boldest explanations of the periodical me- 

 teoric showers, is given in the last number of the French Journal 

 Cosmos, at the occasion of a report of the session of the French 

 Academy; it is founded on the idea of Olbers, I have referred to, 

 and the author supposes that the ehrth in the course of ages has 

 hollowed out for itself a kind of empt}^ rut among those flying 

 meteoric masses, attracting all within the reach of its gravitation; 

 but as from time to time by the periodical inequalities in its orbit 

 and the numberless perturbations to which it is subjected, it moves 

 not exactly in the old rut, it will attract other meteoric masses, 

 thus far escaped its attractive power; the moon as it extends its 

 cruise for a circle around the earth more than fifty of the earth's 

 radii, will of course have a large share of the meteors it meets; 

 coming so much further from the mean track of the rut; she also 

 may send in by her attraction some of the meteors she fails to 

 attract to herself. 



Such a number of dark masses moving about in space may inter- 

 rupt a small portion of the light of some stars, and thus explain 

 some of the irregular periodicities observed in their degree of 

 luminosity. 



If then by the influence of a resisting medium, in space, the 

 planets finally will spirally come nearer to the sun, unite wnth it, 

 may the sun unite with other suns, with which he is now revolv- 

 ing in space around the common centre in the pleyades, and the 

 ■whole present arrangement must come to an end; there is one 

 consolation left, namely, that calculations prove that it will take 

 billions of millions of centuries before such a catastrophe will be 

 accomplished; now these numl^ers a,re entirely beyond the limits 

 of anything we can distinctly conceive, and are at first sight only 

 fitted to overwhelm and confound all our powers of thought; but 

 we must not forget that our conception is rather suited to the 

 wants of common life, of which it is an outgrowth, than to a sur- 

 vey of the universe. The duration of the present form of the 

 universe may be unmeasurably great in our eyes, though demon- 

 strately finite. Sueh enormous numbers are continually brought • 

 under the notice of every one w^ho investigates nature : the small- 

 ness of the microscopic objects, the enormous long duration of the 

 geological periods, all these are expressed by numbers on the same 

 gigantic scale, in comparison with which our space is a point, our 

 time a moment, our millions a handful, and our permanence a 

 quick decay. We are in the habit to contrast the transient fiite of 



