1868.] THE SrOXGE MINUTELY DESCRIBED. 325 



In many places the sponges hold large quantities of the 

 oxide of iron, from the big patches of brown hamiatite that 

 crop out everywhere, and streams of this oxide, as thick 

 as treacle, are seen moving slowly along in the sponge-like 

 small red glaciers. When one treads on the black earth of 

 the sponge, though little or no water appears on the surface, 

 it is frequently squirted up the limbs, and gives the idea of 

 a sponge. In the paths that cross them, the earth readily 

 becomes soft mud, but sinks rapidly to the bottom again, 

 as if of great specific gravity : the water in them is always 

 circulating and oozing. The places where the sponges are 

 met with are slightly depressed valleys without trees or 

 bushes, in a forest country where the grass being only a 

 foot or fifteen inches high, and thickly planted, often looks 

 like a beautiful glade in a gentleman's park in England. 

 They are from a quarter of a mile to a mile broad, and from 

 two to ten or more miles long. The water of the heavy 

 rains soaks into the level forest lands : one never sees 

 runnels leading it off, unless occasionally a footpath is 

 turned to that use. The water, descending about eight feet, 

 comes to a stratum of yellow sand, beneath which there is 

 another stratum of fine white sand, which at its bottom 

 cakes, so as to hold the water from sinking further. 



It is exactly the same as we found in the Kalahari 

 Desert, in digging sucking places for water for our oxen. 

 The water, both here and there, is guided by the fine sand 

 stratum into the nearest valley, and here it oozes forth on 

 all sides through the thick mantle of black porous earth, 

 which forms the sponge. There, in the desert, it appears to 

 damp the surface sands in certain valleys, and the Bushmen, 

 by a peculiar process, suck out a supply. When we had 

 dug down to the caked sand there years ago, the people 

 begged us not to dig further, as the water would all run 

 away ; and we desisted, because we saw that the fluid poured 

 in from the fine sand all round the well, but none came from 



