400 Intelligence and Miscellaneous Articles. 



1. The ring nebula in Lyra, the Dumbbell nebula, the great ne- 

 bula in Orion, and others which might be named, are not, as was 

 but recently believed, extremely remote sidereal clusters ; but their 

 light undoubtedly emanates from matter in a gaseous form. 



2. " According to Lord Rosse and Professor Bond, the brighter 

 parts near the trapezium [in the nebula of Orion] consist of cluster- 

 ing stars. If this be the true appearance of the nebula under great 

 telescopic power, then these discrete points of light must indicate 

 separate and probably denser portions of the gas, and that the whole 

 nebula is to be regarded rather as a system of gaseous bodies than 

 as an unbroken vaporous mass " *. 



3. Progressive changes in the physical condition of certain nebula 

 are clearly indicated by the fact that nuclei have been established 

 which, as shown by their spectra, are not wholly gaseous, but have 

 passed, at least partially, to the solid or liquid form. 



4. The spectroscopic analysis of the light of several comets reveals 

 a constitution similar to that of the gaseous nebulae. 



The spectroscope, then, has demonstrated the present existence 

 of immense nebulous masses, such as that from which Laplace sup- 

 posed the solar system to have been derived. It has shown, more- 

 over, a progressive change in their physical structure, in accordance 

 with the views of the same astronomer. In short, the evidence 

 afforded by spectrum analysis in favour of the nebular hypothesis is 

 cumulative, and of itself sufficient to give this celebrated theory a 

 high degree of probability. — Silliman's^imer/ccw Journal, September 

 1871. 



SOLID CRUST OF THE EARTH. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 Will you be so good as to print this at the end of your next 

 Number after receiving it, in order to correct the following errata in 

 my letter in your August Number, which has just reached Calcutta? 



Page 98, line 13, for column 1 read p. 400, column 1. 



36, after fluid insert and of the fluid on itself. 

 5, for a ead a. 



1 4, for colatitude read codeclination. 

 4, for cos (7—0') read sin (0' — I). 

 21, dV should be added for the attraction of the fluid 

 on itself. But V immediately disappears again from the moments 

 as the centrifugal force does, owing to the symmetry of figure ; and 

 the subsequent calculation and reasoning are not affected. 

 Page 100, line 29, for P, read cP x . 



I am, 



Yours faithfully, 



J. H. Pratt. 

 Calcutta, September 4, 1871. 



* Monthly Notices of the Royal Astronomical Society, voi. xxv. p. 156. 



99 

 100 



