ASTRONOMICAL AND METEOROLOGICAL PHENOMENA. 267 



COMETS. 



Though the larger and brighter comets naturally excite most 

 general public interest, and are really valuable to astronomers, as 

 exhibiting appearances which tend to throw light on the internal 

 structure of these bodies, and the nature of the forces which must be 

 in operation to produce the extraordinary phenomena observed, yet 

 some of the smaller telescopic comets are, perhaps, more interesting 

 in a physical point of view. Thus the six periodical comets, the 

 orbits of which have been determined with tolerable accuracy, and 

 which return at stated intervals, are extremely useful, as being likely 

 to disclose facts of which, but for them, we should possibly have ever 

 remained ignorant. Thus, for example, when the comet of Encke, 

 which performs its revolution in a period of a little more than three 

 years, was observed at each return, it disclosed the important and 

 unexpected fact, that its motion was continually accelerated. At 

 each successive approach to the sun it arrives at its perihelion sooner 

 and sooner ; and there is no way of accounting for this so satisfactory 

 as that of supposing that the space in which the planetary and 

 cometary motions are performed is everywhere pervaded by a very 

 rarefied atmosphere or ether, so thin as to exercise no perceptible 

 effect on the movements of massive solid bodies like the planets, but 

 substantial enough to exert a very important influence on more 

 attenuated substances moving with great velocity. The effect of the 

 resistance of the ether is to retard the tangential motion, and allow 

 the attractive force of gravity to draw the body nearer to the sun, by 

 which the dimensions of the orbit are continually contracted, and the 

 velocity in it augmented. The final result will be that, after, the 

 lapse of ages, this comet will fall into the sun ; this body, a mere 

 hazy cloud, continually flickering as it were like a celestial moth 

 round the great luminary, is at some distant period destined to be 

 mercilessly consumed. Now the discovery of this ether is deeply 

 interesting as bearing on other important physical questions, such as 

 the undulatory theory of light ; and the probability of the future 

 absorption of comets by the sun is important as connected with a 

 very interesting speculation by Professor William Thomson, who 

 has suggested that the heat and light of the sun may be from time 

 to time replenished by the falling in and absorption of countless 

 meteors which circulate round him ; and here we have a cause re- 

 vealed which may accelerate or produce such an event. — Address of 

 Lord Wrottesley, President of the British Association, Oxford, 1860. 



BAROMETERS FOR COAST STATIONS. 



The Duke of Northumberland, as President of the Eoyal National 

 Lifeboat Institution, in connexion with the Meteorological Society of 

 London, has established, under the direction of Mr. Glaisher, F.R. S., 

 and Mr. Sopwith, F.R,. S., a complete series of Stations, not less 

 than fourteen in number, furnished with Barometers. The primary 

 object of the Duke (who generously contributes one moiety of the 

 expense, the remainingfunds being furnished by the Meteorological So- 

 ciety and by subscription) is the saving of life ; but in associating the 



