1889.] Results of a Mission to South Africa. 13 



working a kind of rock quite different to the masses of prehnite in the 

 country which occur in the curious V-shaped troughs, spread over the 

 surface of the land. Well, these things were so extraordinary that 

 they called for very careful examination, and we found that spread 

 over the surface of the land in that district you have volcanic rock, and 

 this volcanic rock has yielded on its decomposition, as a volcanic rock 

 does, a mineral or minerals which consist essentially of decomposed 

 felspar. All volcanic rocks are thus decomposed, and re-crystaliised in 

 combination with a certain amount of water. Wherever the rock is 

 porous, this mineral has entered, with the result that you have a 

 network and nests of occurrences of the mineral, spread through the 

 volcanic rock. Now we are not able to give you the estimate of the 

 quantity of this prehnite, but I may say it is a result of the decay and 

 decomposition of the felspars in the volcanic rock spread over the 

 country. I do not mean to imply that it is a type of the existing 

 surface of the country, but what I would wish you to realise is this,, 

 that in the sea water you have at the present day sea weeds, which 

 sea weeds separate from the sea water a great many mineral salts ; as 

 those sea weeds decay, the mineral salts are deposited on the bottom, 

 and you may be aware of the extraordinary fact that a ship sailing 

 through the ocean collects upon its copper bottom a deposit of gold, 

 which is obtained from the ocean. Well, these salts, which are 

 separated in the sea, come to be embedded in the rock, and when, in 

 process of time, these rocks are compressed a great depth beneath the 

 surface, and are raised in temperature by the compression,- and t 'fre- 

 quently burst away upwards through the fissures produced b the 

 foldings, which become dykes, they are poured out as lava sheets,.. 

 the lava contains the sediments from w 7 hich they were formed. When,, 

 subsequently again, the land which contained these varied mineral 

 salts comes to undergo decay and decomposition, under the effects 

 of the atmosphere, so that enormous thicknesses of rock are 

 cleared away, and nothing but heavy insoluble substance is left at the 

 surface, it results that while many other things are washed away, the 

 gold, if it were originally contained in the rock, is left behind. 

 Although I am not able to tell you the probable quantity of the gold at 

 Cradock, I may say that the gold is there, but not in the 'prehnite in 

 sufficient quantity to make Cradock a rival to the Transvaal just at 

 present. When we went into the neighbourhood of Barkly, we found 

 something new, most interesting to us, in relation to gold ; we brought 

 away specimens to analyse, and the analyses will eventually be placed 

 before you, but I may now mention this, that while a great many of 

 the layers of quartz which are commonly called reefs, which are 

 deposits of quartz, were found to contain gold in combination with iron 

 pyrites, most exlraordinary circumstances were associated with some of 



