2 Transactions of the Boyal Society of South Africa. 
That the intrusion maintains in other districts the chief characters 
described below is borne out by P. A. Wagner The Geology of a Portion 
of the Belingwe District of Southern Ehodesia," Trans. Geol. Soc. 
S. Africa, vol. xvii., p. 49, 1914), who describes similar rocks to those 
encountered at Selukwe. Further, precisely similar rocks have been 
collected at Umvukwe (Gwebi), Makwiro, Ehodesdale, and other places 
situated on the Great Dyke, by G. N. Blackshaw, H. B. Maufe, P. P. 
Mennell, W. Torrance, and the present writer. 
11. — DiSTEIBUTION AND FlELD EeLATIONS. 
In the area examined the intrusion averages some 3 miles wide, but 
varies from 2h to rather more than 4 miles. As will be seen from the 
accompanying map (Plate I), it trends north-north-east to south-south- 
west, and its trend and average width are maintained north and south of 
the portion mapped. 
Its margins are usually parallel to one another. They are gently 
sinuous with here and there conspicuous bulges, a concavity in one 
margin as a rule is reflected as a convexity in the other. A well-marked 
constriction occurs on Helvetia and Adare farms where the intrusion 
truncates the schists which are striking obliquely at it. 
The Great Dyke has intruded into the Granite and along the junction 
of that intrusion with the schistose series (the Greenstone Schists, Banded 
Ironstone, and Conglomerate). 
Along its eastern margin the intrusion is continuously in contact with 
the granite-gneiss with one exception, namely, on Hillingdon farm, where 
a narrow arm of Greenstone Schists, etc., formerly extending from Adare 
farm, has been cut through, and has left fragments in the Great Dyke. 
On the west in the northern part of the area, however, the intrusion is 
continuously in contact with the schists which are metamorphosed by it. 
The Great Dyke, therefore, in this northern part has intruded along the 
former junction of the granite with the schists. The banding of the 
granite on the western margin of the intrusion near the Lundi and 
Amapongokwe rivers strikes diagonally at the margin of the latter. 
Two rivers, the Umtebekwe and Little Tebekwe, flow along the 
marginal portions of the Great Dyke from north to south. This is a 
common feature of the topography produced by the intrusion. The 
streams originally cutting across the mass at right angles, as most of them 
still do, are being diverted by reason of the easily eroded nature of the 
Great Dyke, and now^ tend to flow within it parallel to its sides. 
The tributary spruits flowing into the two main rivers at Selukwe in a 
few places afford sections of the contact of the intrusion and the Gneissic 
granite. In two instances (on Makomisa and Unki farms) tributaries 
