The Work of the Year. 3 



eclipse which shall equal in interest that of July, 1860, there 

 will be in the present year a sufficiency of special subjects to 

 engage astronomers. Let it be an encouragement to amateurs 

 to observe the aspects of the disc of the sun during March and 

 September, that the supposed inter-Mercurial planet Vulcan 

 was first discovered on March 26th, 1859, by Dr. Lescarbault, 

 with means so simple that the discovery stands alone in this 

 respect among the accomplishments of observation. There is 

 the more encouragement, too, that M. Leverrier believes there 

 are many planets circulating within the orbit of Mercury, so we 

 may anticipate successive discoveries to prove the immediate 

 region of the solar orb as thickly peopled as the interval be- 

 tween Mars and Jupiter. Here again is encouragement of the 

 same kind, for of the planetoids, now seventy-one in number, the 

 greater proportion have been discovered by amateurs. The new 

 satellite of Saturn, and the new views obtained of the structure 

 of the rings of that planet, will afford subjects of peculiar 

 interest for observers during the present year. 



From astronomical we turn to cosmical subjects ; and pro- 

 minent among the work of the past year we must place the 

 researches of Dr. Thomson, on the age of the sun's heat, on 

 which a paper was read before the British Association. Dr. 

 Thomson endeavours to show that we have, in the present 

 potential energy of the sun, a measure of its duration, past and 

 present, and, strangely, the conclusions arrived at bear directly 

 on the Darwinian hypothesis. Mechanical energy is inde- 

 structible, but there is ever a tendency to its dissipation, which 

 produces gradual augmentation of heat, cessation of motion, 

 and exhaustion of potential energy by which heat is produced. 

 Some heat is probably produced in the sun by the influx of 

 meteoric matter, and the amount thus generated may be suffi- 

 cient to compensate the loss by radiation. Considerations 

 derived from the disturbances of the inferior planets and the 

 zodiacal light, show that the amount of meteoric matter cannot 

 be enough to give a supply, at the present rate, for 300,000 years, 

 a conclusion ratified by Leverrier by his researches on the mo- 

 tions of the planet Mercury. Considerations of the motions of 

 comets prove that the meteoric matter must be derived from 

 spaces near the sun, the cooling of which, by radiation, cannot 

 be more than l°-4 centigrade annually. Adding chemical con- 

 siderations to those of a strictly astronomical character, he 

 concludes that the sun cannot have illuminated the earth for 

 100,000,000 years, and it is certain it has not done so for 

 500,000,000 years. Therefore the conditions nnder which fife 

 has passed through its successive phases on this planet, have 

 not been in continuance long enough to insure the results de- 

 manded by prevalent theories of organic transmutation. In 



