248 Comets. 



private, and increased by planting in Loch Swilly. Irish 

 oyster-dredgers have a notion that the more the banks are 

 dredged, the more the oysters breed.* 



Comets — Great Number of Becorded Comets — The Number of 

 those unrecorded probably much greater — General Descrip- 

 tion of a Comet — Comets without Tails, or with more than 

 one — Their extreme Tenuity — Their probable Structure — 

 Motions conformable to the Lam of Gravity — Actual Dimen- 

 sions of Comets — Great Interest at present attached to Come- 

 tary Astronomy, and its Seasons — Femarks on Cometary 

 Orbits in general. 



In the admirable Outlines of Astronomy, by Sir John F. 

 W. Herschel, just published, where all is excellent, we were 

 deeply interested with the account of those wonderful mem- 

 bers of our system — the Comets. From this masterpiece of 

 thought and writing, we now lay before our I'eaders the fol- 

 lowing extracts :t — 



The extraordinary aspect of comets, their rapid and seem- 

 ingly irregular motions, the unexpected manner in which 

 they often burst upon us, and the imposing magnitudes which 

 they occasionally assume, have, in all ages, rendered them 

 objects of astonishment, not unmixed with superstitious dread 

 to the uninstructed, and an enigma to those most conversant 

 with the wonders of creation, and the operations of natural 

 causes. Even now, that we have ceased to regard their 

 movements as irregular, or as governed by other laws than 

 those which retain the planets in their orbits, their intimate 

 nature, and the offices they perform in the economy of our 



* The above observations are from Part XX. of Messrs Forbes and Stanley's 

 valuable History of Br'tish MoUusca. To those interested in the natural and 

 oeconomic history of the common oyster, we recommend the perusal of a paper 

 on the Danish Oyster-Beds, by M. II. Kroyer, at page 28 of vol. xxix. of this 

 Journal. 



t Outlines of Astronomy. By Sir John F. W. Herschel, Bart., &c. &c. &c. 

 1 vol. 8vo, pp. 6l51. London : Longman, Brown, Green, and Longmans ; and J. 

 Taylor. 1849. 



