Horticultural Society. — Astronomical Society. 457 



ing of the Geological Society, and for a detail of the beds 

 which form the cliffs from Gris-Nez to Equihen, to an account 

 of the lower Boulonnois, to be read at a future meeting. From 

 Equihen to the mouth of the Somme, the coast is altogether 

 occupied by dunes of sand, the sand-hills being in some 

 places, especially in the vicinity of Etaples, more than 100 feet 

 in height. These hills are in general somewhat crescent- 

 shaped, the back of the crescent being turned towards the 

 prevailing wind, and the slope on the lee-side much more 

 rapid than the opposite one, The immediate base of the 

 dunes seems to be peat, which is found both on the land 

 side of them, and without, just on the verge of the sea, and 

 in some places below the level of high water : but no rocks 

 have yet been discovered along the coast beneath the dunes. 

 A list of heights obtained by the barometer is subjoined to 

 this paper, and some detached sketches are annexed to it of 

 interesting geological appearances on the French shore. 



HORTICULTURAL SOCIETY. 



June 1. — A paper by the Hon. and Rev. Wm. Herbert, 

 containing " Further Observations on Hybrid Plants," was 

 read. 



June 15. — Flis Imperial Majesty the Emperor of Russia 

 was elected a Fellow of the Society. 



The following communications were read : 



Description of a Melon Pit on a new construction. By 

 Richard Lacy, Esq. 



On the best Means of Protecting the Blossoms of Trees 

 on Walls. By the President. 



ASTRONOMICAL SOCIETY. 



June 11. — The following papers were read: — 

 1st. On the Variation of the mean Motion of the Comet of 

 Encke produced by the Resistance of an Ether ; by M. Mas- 

 sotti. This comet is well known to evince a diminution of its 

 periodic time at each revolution, and the object of this paper 

 was to demonstrate the cause of this effect. Encke himself 

 supposed it was occasioned by an ether diffused through space; 

 but if so, how happens it that the planets also have not been 

 retarded ? This the author attempted to show might be the 

 case, although the phenomenon might pass unobserved. He 

 adopts with Encke, the hypothesis of Newton, that the density 

 of this ether diminishes in the inverse ratio of the square of the 

 distance from the sun; consequently that the planet Mercury 

 would be most likely to be affected by it ; and by a long series 

 Vol. 63. No. 314. June 1824-. 3 M of 



