136 REPORfg on Tiifl s'tate of science. 



8 to 11. I have no right to vote on the relative value of alternative 

 local terms. 



In a subsequent letter, June 11, Sir T. H. Holland adds the 

 following : — 



' It is not exactly correct to state that the "Witwatersrand System 

 would be the South African equivalent of the American Algonkian, as 

 this term is employed in America to include, besides the comparatively 

 unaltered Keweenawan and Animikie Series, the foliated and closely 

 folded (Lower) Huronians. The use of. a system name to straddle 

 across one of the greatest breaks known, namely, that between the 

 (Lower) Huronians and the Animikies, is enough to condemn the term; 

 but, as it has been used so commonly in this way, it would be 

 impossible, now to use the term in South Africa ; for the Swazi- 

 land Series, according to Hatch and Corstorphine, 1 evidently in- 

 cludes rocks that would be included in the American Algonkian. 

 If the term Algonkian had been made to extend from the base 

 of the Cambrian to the epi-Huronian, infra-Animikie unconformity, 

 it would have had an extended use in stratigraphy ; but it is too 

 late now to change its meaning. If, therefore, no suitable local term 

 can be devised for the pre-Palaeozoic rocks lying unconformably on the 

 Swaziland schists and gneisses, the Indian name Purana might be 

 borrowed; it covers all old unfossiliferous rocks (in part or wholly pre- 

 Cambrian) down to the base of the oldest rocks resting unconformably 

 on the gneisses, schists, and closely folded, metamorphosed Dharwar 

 (Lower Huronian) Series. 



' For all rocks below this great break I use the term Archaean in 

 India, and, although this use of the term is not exactly that proposed 

 by Dana (who evidently intended originally to include the unmetamor- 

 phosed pre-Palaeozoic sediments), it corresponds to the recognised use 

 of the term in Canada, and to the meaning adopted by Van flise in his 

 memoir on the " Iron-Ore Deposits of the Lake Superior Region. " (21st 

 Ann. Eep. U.S. Geol. Surv., Part III.); that is, after he had published 

 other views in his well-known Bulletin No. 86 on the Archaean and 

 Algonkian. 2 



' It is true that local unconformities between the (Lower) Huronian 

 (Dharwarian of India) and the older gneisses are shown by conglom- 

 erates, and possibly in time the Archtean may be subdivided locally to 

 recognise these. But, although these conglomerates, that include 

 pebbles of gneiss, indicate a pre-existing gneissose series, there are many 

 granitoid gneisses in the complex that are younger than the associated 

 Dharwars (and- — Lower — Huronians). Hence it is possible to split up 

 the Huronian-Laurentian (Archaean) complex only locally, and this fact 

 should be contrasted with the great widespread unconformity above the 

 group composed of the basal complex and (Lower) Huronian 

 (Dharwarian) rocks. 



' Lithologically the Dharwars in India can be distinguished from the 

 more crystalline gneisses and schists with which they are folded, just 

 as the Huronians (Lower Huronians) can generally be separated from 



1 Geology of South Africa, 1905, p. 101. 



» See discussion by C. K. Leith, Journ. Qeol, x., 1602, p. 894. 



