38 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



light is nearly insensible ; and, following out the suggestion 

 given by Fizeau, Stephan has applied to the Marseilles tele- 

 scope a diaphragm having two apertures for the observa- 

 tion of the fringes produced by interference. If the star has 

 a certain diameter, the fringes will disappear altogether; 

 and if its diameter is zero, the distances of the frino-es will 

 vary with the distances of the two apertures in the dia- 

 phragm. The results of Stephan's limited number of meas- 

 ures thus far taken is that Sirius appears to have a measura- 

 ble diameter. He hopes to continue his observations. 6 B, 

 1873, 1008. 



THE NEBULAR THEORY. 



Professor Peirce has communicated to the recent meeting 

 of the American Association for the Advancement of Science 

 the result of some of his investigations into the development 

 of the solar system, according to the nebular hypothesis of 

 Laplace. He considers that the actual rotation of the planets 

 on their axes is explained on the supposition that they were 

 formed from rings thrown off from the rotating central body, 

 or sun, in the process of condensation. The inner portion of 

 such a ring, having a less velocity than the outer portion, the 

 axial rotation would necessarily follow the breaking up of 

 the ring. Professor Peirce even is able by mathematical 

 analysis to show that the velocity of the rotation of Jupiter 

 and of Saturn is precisely such as would result from these the- 

 oretical mechanical considerations. Proc. of the Portland 

 Meeting of the Amer. Assoc, for the Advancement of Science. 



THE STABILITY OF THE SOLAR SYSTEM. 



Mr. Stockwell, in a memoir published by the Smithsonian 

 Institution, gives the result of some laborious researches on 

 the secular variations of the planetary orbits. The inequal- 

 ities in the planetary motions that depend upon the variations 

 of the elements of the elliptic orbits in which they move re- 

 quire an immense number of years for their full develop- 

 ment, and are called secular inequalities. The determina- 

 tion of the periodic inequalities has hitherto received more 

 attention than has been bestowed upon the secular inequal- 

 ities. This is owing in part to the immediate requirements 

 of astronomy, and also in part to the less intricate nature of 



