338 ANNUAL OF SCIENTIFIC DISCOVERY. 



quantity of movement of rotation, the past and present radii of percus- 

 sion, the primitive diameter of the generating surface of the rings, and 

 the present dimensions and density of the planets, have been regulated 

 by a general law, which has fulfilled for all of them the four fundamen- 

 tal conditions of Kirkwood's hypothesis. 



" We may extend the nebular hypothesis and Kirkwood's analogy 

 to the secondary systems. If they are laws of nature, they must apply 

 to both. In the secondary systems, the day and month are the same. 

 This fact has remained hitherto unexplained. Lagrange showed that 

 if these values were once nearly equal, a libration sets in round a state 

 of perfect equality; but he offered no conjecture as to the cause of the 

 primitive equality. On the nebular and Kirkwood's hypothesis, it would 

 only be necessary that, upon the breaking up of the ring, the primitive 

 diameter of the generating figure and law of relative density of layers 

 should be preserved." 



Prof. Peirce, whose opinion will probably be regarded as of more 

 value on such a subject than that of any other man in this country, 

 especially since his successful discussion with Leverrier, remarked, that 

 Kirkwood's analogy was the only discovery of the kind since Kepler's 

 time, that approached near to the character of his three physical 

 laws. Bode's law, so called, was at best only an imperfect analogy. 

 Kirkwood's analogy was more comprehensive and more in harmony 

 with the known elements of the system. The diameter of the 

 sphere of attraction, a fundamental element in this analogy, now for 

 the first time gave an appearance of reality to Laplace's nebular hy- 

 pothesis, which it never had before. The positive testimony in its fa- 

 vor would now outweigh the former negative evidence in the case, 

 however strong it may have been. It follows at least from Kirk- 

 wood's analogy, that the planets were dependent upon each other, 

 and therefore connected in their origin, whatever may have been the 

 form of the connection, whether that of the nebular hypothesis, or 

 some other not yet imagined. 



At a later period of the meeting, Mr. B. A. Gould, Jr., stated that 

 he had gone through the necessary calculations, using different quanti- 

 ties, and had come to the same conclusions as Mr. Walker. He ex- 

 pressed his opinion, that at some future day the world will " speak of 

 Kepler and Kirkwood as the discoverers, of great planetary laws." 



The members generally expressed the opinion, that Laplace's neb- 

 ular hypothesis, from its furnishing one of the elements of Kirkwood's 

 law, may now be regarded as an established fact in the past history of 

 the solar system. 



SHOOTING STARS OBSERVED IN 1849. 



THE following observations on the periodical occurrence of shooting 

 stars have been made in various parts of the country during the year 

 1849. On the night of the 20th of April, 54 different meteors were 

 observed in New Haven, as follows : in the northwest, 23 ; in the 

 south, 21 ; in the northeast, 10. There was nothing remarkable in 

 these as to. brilliancy, nor was there any decided point of radiation. 



