106 
THE GEOLOGIST. 
■west 38° 15' northward, and to the cast 38° 15' south; thirdly, that 
the veins in question are generally encased in the primitive rocks 
(granite, gneiss' mica-schist, talc-schist, &c.), never occurring higher 
than the Silurian strata, properly so called, and belonging, therefore, to 
a very ancient system of dislocation. Our readers will readily appre- 
ciate all the importance and utility attached to these investigations. 
The author of the third letter, dated Copiapo, the 16th September, 
1857, is from M. Pissis ; it relates to a geological exploration of some 
parts of Chili. The writer informs us that he is, at present, studying 
the province of Atacama, of which he hopes to have a geological map 
completed before the end of 1858. The stratigraphical characters of 
the southern parts of Chili bear a great resemblance to those of the 
Brazils, and the upheaving of the strata seems to belong to the Humls- 
ruclc system ; the direction of which, in Chili, is north-east and south- 
west, which is also that of the granite and talc-schist of the countrJ^ 
But, independently of this, there is a large band, from fourteen to 
eighteen leagues wide, of other formations running parallel to the coast, 
some of the strata of which are remarkable for the abundance and 
beautiful preservation of their fossils. The working of silver and 
copper mines is becoming every day more and more active there, not 
only in the inhabited districts, but even in the desert. 
A short time ago, in the year 1856, an Englishman residing in 
South America, but whose name we cannot think of at this moment, 
discovered the presence of silver in the water of the Atlantic Ocean. 
He was surprised to find a small quantity of silver in the copper- 
sheeting of vessels which had navigated for some time. He analysed, 
first the new copper before it was placed on the ships, then the old 
copper taken from the bottom of ships that were undergoing repair. 
The results of his experiments were, that the copper taken from ships 
that had navigated during the longest period of time contained the most 
silver; those which had only made short voyages contained very little 
more silver than that which was originally found in the new copper- 
sheeting.* Similar experiments were lately made in Prance by MM. 
Durocher and Malaguti, whose conclusions coincide with those arrived 
at in South America. The existence of silver in sea-water cannot 
therefore be doubted. The presence of this precious metal in the 
waters of the ocean is without doubt due to the property possessed 
by common salt (chloride of sodium) of dissolving chloride of silver — 
■-• Which almost always contaiilB slight ijuantities of silver. 
