4i6 



E. C. HARDER AND R. T. CHAMBERLIN 



of quartzite (Fig. 21). Many of these troughs reach a depth of 

 30 meters or more, though some of the deeper ones scarcely exceed 

 100 meters in width (Fig. 22). No determination has been made 

 of their maximum width, while as to their original longitudinal ex- 

 tent nothing is known. From their irregular occurrence and their 

 relation to the underlying quartzite it is presumed that these 

 deposits are for the most part the result of stream deposition. 



Fig. 21. — The pit of Serrinho. A shallow depression in the Carafa quartzite 

 which was partially filled with diamond-bearing conglomerate. The conglomerate 

 and beautifully white kaolin are seen in the bottom of the excavation. The final 

 washing operations to recover the diamonds are conducted in the batea, or jig, under 

 the thatched roof. 



This view is further strengthened by the nature of the materials 

 composing them and the relation of the different kinds of material 

 to each other. By detailed mapping it might be possible to con- 

 nect all these remnants so as to reproduce the old drainage network 

 as it was when the conglomerate was deposited. 



The gravel, sand, and clay occur associated in the deposits as 

 beds, lenses, or masses, without any regularity. Locally beds of pure 



