part 1] and associated rocks of Mozambique. Sl> 



results are sufficient to justify a broad correlation of the Pre- 

 Cambrian rocks concerned into Lower and Middle Groups. In 



Table XII. 



Lead-ratios. Hocks and Localities. Geological Age. 



0'04 Pegmatites of Appalachians, U.S. A Late Carboniferous. 



Urauiaile from St. Ives (Cornwall) Do. do. 



O'Oo Pegmatites ot Langesundijord (Norway) . Devonian. 



006 Balangoda pegmatites, Ceylon Unknown. 



0-07 

 0-08 



009 Morogoro pegmatites, G.E. Africa Upper Pre-Cambrian (?) 



o-io 



Oil 



0-12 



0"13 Pegmatites of Moss District (Norway). "^ 



0*14 Singar pegmatite, India. 



0"15 Nrassi, Monapo, and Ligouia granites, Middle 



Mozambique. }> Pre-Cambrian. 



0*16 Ytterbv pegmatites, Sweden. 



- 17 Villeneuve pegmatite, Canada. 



Pegmatites of Arendal district (Norway). J 

 018 

 0-19 

 0-20 



0*21 Gneis^ose granite, M< zambique. "^ 



022 I Lower 



0-28 [Pre-Cambrian. 



0"24 Sebastopol pegmatite. Canada. J 



every case where independent geological evidence is on record, it is 

 in complete accordance with the implications of the lead-ratios, 

 as regards both position and sequence. Where geological 

 evidence is lacking, the lead-ratios may, therefore, be 

 used as a general guide to correlation. 



XI. O-RIGIX OF THE INSELBERO LANDSCAPE. 



The inselberg type of landscape is a striking characteristic of 

 many parts of Africa. It has been described by W. Bornhardt 1 

 in German East Africa ; bv S. Passaree 2 in South -West Africa and 

 Adamaua ; by Dr. J. D. Falconer 3 in Northern Nigeria : and most 

 recently by Dr. E. O. Teale & Mr. K, C. Wilson 4 in the Territory 

 of the Companhia de Mozambique. Everywhere it has been deve- 

 loped in areas over which long-continued denudation has exposed 

 the basement-rocks of the African continent ; rocks which, as in 



1 ' Die Oberflachengestaltung & Geologie Deutscb-Ost-Afrikas ' vol. vii, 

 Berlin, 1910, pp. 34-39. 



2 (a) 'Adamaua' 1895: (6) 'Die Kalahari' Berlin, 1904; (c) ' Ueber 

 Bumpfflachen & Inselberge ' Zeitschr. d. Deutsch. Geol. Gesellscb. vol. lvi 

 (1904) Prot. pp. 193-209 ; (d) ' Die Inseiberglandschaft in tropischer Afrika ' 

 Nat. Wochenschr. n. s. iii (1904) pp. 657-65. 



:i Rep. Brit. Assoc. (Dundee, 1912) 1913. p. 476 ; see also ' Geology & Geo- 

 graphy of Northern Nigeria ' London, 1911. 



4 Geogr. Journ. vol. xlv (1915) p. 16: see also A. Holmes & D. A. Wray, 

 ibid. vol. xlii (1913) p. 143. and W. M. Davis. ' The Geographical Cycle in 

 an Arid Climate' Journ. Geol. Chicago, vol. xiii (1905) p. 381. 



