70 Proceedings of Philosophical Societies. [July, 



lie on the sea-shore on the north coast of Devonshire. They 

 are precipitous, and about 140 feet high. They consist of 

 alternate beds of grey wacke and grey wacke slate, the first of 

 ■which is called dimslone, the second shillat. This rock only 

 contains organic remains where it alternates with transition 

 limestone. Killas is considered by the author as clay slate. It 

 is traversed by frequent veins of a porphyritic rock, which does 

 not enter into the grey wacke, contains sometimes topaz, and 

 frequently garnet. Its veins are often filled with chlorite, mica, 

 and crystallized felspar, and also contain tinstone, grey cobalt 

 ore, &c. 



A paper on the Island of Staffa, by Dr. Macculloch, was also 

 read. This island is about two miles in circumference. It 

 forms a kind of table land, bounded on all sides by steep cliffs, 

 from 60 to 70 feet above high water mark. The highest eleva- 

 tion of the island is 120 feet. The whole island is a mass of 

 basalt.* The basalt occurs in two states, columnar and amor- 

 phous ; the latter is usually amygdaloidal, and contains zeolites. 

 On the south-western side of the island there appear to be three 

 distinct strata of basalt ; the lowest is amorphous ; the second 

 is from 30 to 50 feet thick, and consists of those columns which 

 constitute the conspicuous feature of Staffa. The uppermost 

 stratum consists of small columns. The surface of the island is 

 covered in many places with rounded fragments of granite, 

 gneiss, mica slate, quartz, and red sandstone, together with a 

 few rolled pieces of basalt. 



( To be continued.) 



IMPERIAL INSTITUTE OP FRANCE. 



Account of the Labours of the French Institute for 1812. 



(Continued frem Vol. I. p. 396.) 

 BOTANY AND VEGETABLE PHYSIOLOGY. 



Most physiologists have long admitted in plants an ascending 

 sap, winch mounts from the roots to the branches, and contri- 

 butes to the increase of the branches in length; and a descending 

 sap, which goes from the leaves to the roots, and to which some 

 persons ascribe the chief part of the growth of the wood, and 

 of course the increase of size in the trunk. 



M. Feburier, a cultivator at Versailles, has endeavoured to 

 collect these two saps separately. For this purpose he bored a 

 deep hole in the trunk of a tree, and fixed a bladder upon the 



« From specimens of Staffa shown mc by Lieut. Col. Fullerton, which he 

 brought himself from the island, I am inclined (o consider the rock not as 

 basalt, but as porphyry slate. [Note of the Editor.] 



