Green Sands 135 



attributing this to the escape of air enclosed in cavities and 

 acted on by heat that had passed through the ice. He 

 (the speaker) had compressed a quantity of snow into ice 

 like that of a glacier, and then by heating it obtained the 

 results observed by Agassiz. 1 Such ice also showed a veined 

 structure at right angles to the pressure, and this structure 

 was sometimes exaggerated into a true cleavage. 



Dr. Carpenter gave the results of his studies of the green 

 grains in ' Greensands,' which he had found in rocks as far 

 back as Silurian, and which proved to be casts of f oraminifera 

 made by a greenish, siliceous material. He gave particulars 

 of the cast of a curious Orbitolite, the calcareous part of which 

 had disappeared, as is well shown in Ehrenberg's figures. 2 



Sir R. Murchison observed that the Greensands were a 

 good example of the value of Palaeontology, for it had proved 

 those near St. Petersburg to belong to the Silurian Period, 

 which Brongniart had supposed to be Tertiary. 



At the 94th meeting (May I4th) Dr. Barth 3 was a guest, 

 and gave an account of Timbuctoo. The people are such 

 strict Mohammedans as to forbid the use of tobacco. To 

 that creed they had not long been converts, for it was forced 

 upon them by the Fulahs, a warlike race of Arabs, which had 

 subdued a great part of Central Africa. The natives are 

 not true negroes, their hair is not woolly, and they show 

 an affinity, like the Madagascar people, to the Malays. 

 They are intelligent, but speak an unwritten dialect, Arabic 

 being the learned language, in which histories exist, of 

 both Timbuctoo and Bornou, that go back to the fifteenth 

 century. They are giving way to the Tuaregs, who exact 



1 See Glaciers of the Alps, part ii. sect. 5 (1860), and Hows of Exercise in 

 the Alps (1873), pages 362-8. 



2 See W. B. Carpenter, The Microscope and its Revelations (Dallinger's 

 Ed.), page 827, note. 



3 Heinrich Barth (1821-1865), a German, ' One of the greatest modern 

 scientific travellers,' began his journeys in countries near the Eastern 

 Mediterranean in 1845. In 1850 he started from Tripoli and explored 

 thence to Adamawa in the south and from Bagirmi in the east to Timbuctoo 

 in the west, returning to Europe in 1856. His great work, Travels and 

 Discoveries in Central Africa, was published 1857-8. 



