November 17, 1893.] 



SCIENCE 



ayi 



that once were enclosed in the moutonned ridges, and 

 subsequently eroded therefrom. The grold is believed to 

 be in quantity sufficient to be profitable to mining opera- 

 tions, especially because the mining could be done econom- 

 ically by water, which is convenient, abundant, and has 

 a rapid fall or descent in the nearby creeks. 



The alluvial beds of auriferous clays, sands, gravels, 

 and small boulders that are found in the beds of some of 

 the gulches and in the channels of some of the present 

 system of creeks are often partly cemented by hydrous 

 oxide of iron in some places and by silica at other local- 

 ities. These deposits were commenced, I am persuaded, 

 during the Terrace epoch, and, in some places, are appar- 

 ently quite rich in gold of rough, semi-angular pieces and 

 in rounded particles; yet some of the particles of gold 

 in the small creeks or nearby dry gulches appear so 

 angular and undisturbed at their edges as to impress 

 one with the opinion that they have increased in 

 size, "grown," where they are discovered by additions 

 from passing solutions containing gold; the chief sources, 

 however, of the gold found in these creeks are the same 

 as those named under the head of reefs or lodes, with ad- 

 ditions of gold from the older leads above described 

 found in the upper, and appai-ently j^assing through the 

 erosion-formed hills and from accretions of gold deposited 

 from passing auriferous solutions. The bedrock in some 

 of the creeks is an iron-cemented arenaceous argillyte 

 resting on a bed of partly cemented boulders, sands and 

 clays which appear, at one place discovered, probably in 

 the entire locality, to rest on strata of auriferous con- 

 glomerates or breccia and this on an auriferous gravel 

 superimposed on a bedrock of metamorphosed shale or 

 slate. 



Greological history. We found several obstacles inter- 

 vening to prevent, at present, that careful examination 

 necessary to determine the geological epoch, when these 

 granite ridges were upheaved and when thereafter they 

 were exposed by the denudation of superimposed strata; 

 during what epoch the regional elevation occurred and 

 the erosion-sculptured hills in that region were formed; 

 from what rocks or sources came the gold found now in 

 the reefs or lodes traversing, longitudinally, the moun- 

 tains and ridges. 



One obstacle is that no ravines or caiions were discov- 

 ered that deeply enough expose the strata toward the 

 centre of the mountains or ridges. 



Other obstacles are, the very deep disintegration, in situ, 

 of the exposed rocks and the deep soil covering the sur- 

 face and also the dense vegetation, frequently a jungle 

 difficult to cut a pathway through, covering in matted 

 masses even the nearly perpendicular sides of ravines; 

 but, tentatively, and from the clearest examinations we 

 could make, we form the following geological history of 

 this locality. 



1. The granite in the hills and ridges was forced up 

 through Jurassic period and later rocks and it upturned 

 to nearly vertical the sup)erimposed strata, in some of 

 which strata were discovered moulds of silica (lined with 

 small crystals of quartz) like the Trigonia Conradi, also 

 others like moulds of Tancredia Warreniana. 



The fissures, also the dykes of diorite, appear to have 

 resulted from disturbances occurring in epochs Post- 

 Oolitic, but not extending later than the Cretaceous, this 

 being the latest known or generally recognized time or 

 period during which gold has been conveyed in large 

 quantities or percentages, as a constituent in granites and 

 diorites, up to the earth's crust; these auriferous granites 

 and diorites are certainly abundant in this region and are 

 not Palaeozoic nor Cenozoic rocks. The gold in the reefs 

 or lodes has been dissolved from the granites and 

 diorite rocks by hot mineralized waters and deposited 



therefrom into the fissures or reefs, on cooling or on de- 

 oxidation of the solutions, either enclosed in pyrites or as 

 free gold. 



The gold in the placer mines, drifts or leads, appears 

 to have been derived almost entirely from the disinte- 

 grated and denuded granites forming the mountains and 

 from the reefs in the mountains; a small percentage of the 

 alluvial gold is, however, from the small areas or patches 

 of auriferous quartz eroded from the moutonned ridges, 

 also a small percentage of gold has been deposited from 

 passing alkaline waters that contain gold in solution.'' "• 



The patches of auriferous quartz found generally at the 

 base of the moutonned ridges as if eroded from them ap- 

 pear to have been transported (with the other materials 

 composing the moutonned ridges) from auriferous reefs 

 in the ridges forming the southeastern part of the Mata- 

 galpa system of mountains. 



The boulders of bluish-colored rocks, auriferous and 

 containing a large percentage of pyrites, found quite fre- 

 quently in that region, are usually some variety of the 

 soda-bearing hornblede rocks like glaucophanyte, although 

 bluish trachytes, also bluish hypersthene boulders, 

 so:ne of them auriferous (probably all of them) were dis- 

 covered. Some of the very interesting observations noted 

 were: (a) The altitude above the Caribbean Sea (aneroid 

 readings) of several of the hills and ridges in the region 

 herein described is from 1,000 to 3,600 feet, consequently 

 the flow of water to the Caribbean Sea, only 90 or 100 

 miles distant, is very rapid, there being no swamps, only 

 those of brackish water in the delta of the rivers; this 

 rapid descent of water from the mountains over numerous 

 rapids, cascades and falls in the creeks and rivers offers 

 many places where great water power or pressure could 

 be had to move machinery for sawing logs, defibrenating 

 plants, mining, etc. ; (6) That region, excepting the clay- 

 surfaced moutonned ridges, is covered, from two to twelve 

 or more feet deep, with a very fertile soil composed in 

 large percentage of partly decomposed vegetable matter 

 (nitrogenous) and potash and other alkalies and alkaline 

 earths, from the alkali-containing rocks, granite, feld- 

 spar, etc. Consequently there are excellent agricultural 

 lands for corn, potatoes, coifee, tobacco, almonds, etc., on 

 the sides of the hills and ridges, and suitable for sugar 

 cane, plantains, bananas, cacao, India rubber trees, etc., 

 in the valleys. Some of the mountain lands are admir- 

 able for coffee, and in the upper valley lands, indigenous 

 cacao trees (Theobroma) of good varieties are numerous; 

 (c) The climate is warm, but not uncomfortable, no 

 lagoons nor swamps in the hilly region ; (d) On the moun- 

 tain ridges grow forests of large trees, among which ma- 

 hogany, cedar, rosewood, sapote (Ulva sylvestra), iron 

 wood, guanacaste and nispero appear to be the most nu- 

 merous. 



The tunoo trees' are also numerous and of large size, 

 and, young vigorous-growing India rubber trees (Sypho- 

 nia elasticos) are very abandant, while in shaded moist 

 places, the surfaces of disintegrating rocks are fre- 

 quently covered with the beautiful velvet vine of Nicar- 

 ragua (first discovered about 1856 in Nicaragua), having 



°GoId being invariably found in the granitic series of rocks, especially 

 those of PalEEOzoic and Mesozoic eras and early Tertiary period, should, I am 

 Inclined to believe, influence us to recognize^the gold as a constituent and 

 not merely an accessory mineral in the rock. 



"The fact of the existence of gold in rocks of the granite series appears to 

 give support to the theory of the successional deposition of the elements in 

 the earth, those of greatest sp. gravity being nearest to the earth's centre. 

 Platinum, gold and iron appear to' have been brought to the crust of the 

 earth in every upheaval of granitic masma. 



^Tlie tunoo'e.Kudes freely, when scarified, a milky juice appearing like the 

 milk or sap that flows from lacerations in an India rubber tree, but concretes 

 into a gum like gutta percha. The fibrous inner bark is a texture of strong 

 interwoven fibres and can be removed from the tree in pieces as wide as the 

 circumference of the tree (from three to si.x or six and a half feet wide) and 

 twenty to forty feet long. The Soomoos and Sambos use this bark as bed- 

 clothing and as clothing for their bodies; they prepare the bark for these 

 purposes after removing it from the tree by wetting in water and softening 

 by beating it with .sticks, when it beconu-s soft and remains very strong. 



