GEOLOGY. 267 



rock. After crossing the Yumari, we first enter the gold fields of 

 the country. 



Gold veins occur in brecciated and other slates, which are but 

 little changed from the sedimentary and fossiliferous condition. 

 These slates appeal" to be changed in places into talcose rock, and 

 then auriferous veins are more abundant. The more silicious 

 portions are changed into porph^Toid rock, and dioritic rock is 

 frequent. 



The best-known portion of this gold field is the valleys of 

 Mocnpio and Iguana. The whole country south of the Imitaca 

 may be called auriferous, for gold is found in all the streams, tuid 

 on the savanna. In the Mocupio gold is found, — 



1st. In the beds of streams, in sands and gravel. 



2d. In placer deposits, under cover of earth-, clays and 

 gravels. 



3d. In red earth, within a few feet of the surface. This is 

 often very rich. A nugget weighing 15 pounds was found 

 in it. 



4th. In conglomerate of recent formation, 



The geographical area which is auriferous is very great, reach- 

 ing through the English, Dutch, and French Guitmas, and through 

 all of VenezueUan Guyana. 



It should be called the " Parima Gold Field." 



Difference of Level between the Bed Sea and the Mediterranean. — 

 M. Foiree, Inspector General, discusses this question in the 

 ** Comptes Rendus " of Aug. 2, 1869. He says : — 



'* It results from the comparison of the level of 1799 with that 

 of 1856, adopted by the international commission, that the Red 

 Sea is 0.86™ higher than the Mediterranean." 



The borings for rock salt near Wylen, Switzerland, have given 

 very favorable results. Near the Rhine, a bed of 80 feet in thick- 

 ness has been found at a depth of 420 feet below the surface, and 

 another, 50 feet thick, not far off. The salt is hard, pure, and of 

 excellent quality. 



Sea Depths. — Soundings for sul)marine cables show that the 

 Baltic, between Sweden and Germany, is 125 feet deep ; the Adri- 

 atic, between Venice and Trieste, 130; the English Channel, 300; 

 the Irish Sea, in the south-western part, 2,000 ; the Mediterranean, 

 east of Gibraltar, 3,100 ; off the coast of Sx^ain, 6,200 ; by the Cape 

 of Good Hope, 15,500. 



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