212 JOSEPH THOMSON ON THE GEOLOGY OF [May 1899^ 



this way the traveller crosses the glen of the 'Wad Msira, and then 

 iinds himself, after ascending a little, at the commencement of a 

 long shallow valley trending southward and draining into the Wad 

 Sus. Again are the valley and the junction of the two formations 

 coincident, and moreover the junction marks a line of fault where the 

 metamorphic rocks have been thrust up, to the disturbance of the 

 Cretaceous Series along the line of upheaval. The last-named rocks 

 have been tilted at various angles, while a short distance from the 

 fault the beds are scarcely disturbed from their horizontal position. 



South-west of the village of Ida Uziki the Atlas begins to tail 

 off very rapidly, but here again recurs the same characteristic 

 upheaval of the metamorphic rocks without disturbance of the 

 general horizontality of the red sandstones and shales — except along 

 the immediate line of uplift, where, of course, the Cretaceous rocks 

 have been much disturbed and carried up on the flanks of the 

 upheaved metamorphic series. 



The glen of the Asif Ig marks the end of the Atlas range, for here 

 that range not only merges into the general level of the plateau, 

 but the metamorphic rocks finally disappear beneath the Cretaceous. 



Discussion. 



The President explained that the manuscript of the foregoing 

 communication was found, in 1898, among some of the papers of 

 the late Mr. Topley, and was handed over by his son to the speaker. 

 The name of the author did not appear to be marked on it, but the 

 initials ' J. T.' were inserted below some faint pencil-marks on a 

 wrapper. He thought that it must have been written by that able 

 observer, the late Joseph Thomson, and, on its being shown to 

 Dr. Scott Keltic, Secretary of the Eoyal Geographical Society, 

 he at once identified the handwriting. 



On comparing the manuscript with Thomson's book and paper, 

 Proc. Eoy. Geogr. Soc. vol. xi (1889) pp. 1-16, it was found that 

 though various geological notes were scattered through these, the 

 present communication contained much more than these notes, and 

 it also has the advantage of putting all together. He thought 

 therefore that it should be read before the Geological Society, espe- 

 cially as Morocco is a country of which so little is known. 



Mr. Gibson said that, as a student of African geology, he 

 felt impelled to bear testimony to the Author's excellent geo- 

 logical work in Africa. His notes on the geology of the routes 

 traversed by him in the Great Atlas and Southern Morocco were an 

 acceptable addition to the knowledge of these little-known regions. 

 The absence, so far as yet shown, of older or younger Palaeozoic 

 formations on the flanks of the Atlas is noteworthy, as these deposits 

 are well represented south of that chain. The east-and-west faults 

 mentioned in the paper are parallel to the main lines of dislocation 

 in Algeria. 



Prof. Hull felt grateful to the President for rescuing this 

 important paper from oblivion and bringing it before the Society^ 



