. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 18-4 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. Station is reached, where the stream of the same name has cut down through the clays to a black rock similar to that of Bujio. At Tavernilla Station (Colon miles) the Canal Company has cut into a small hill apparently composed of red clay. At its base is the first undoubted exposure of a peculiar rock which may be called tem- porarily the Barbacoas formation. At Barbacoas (Colon 23 miles) the railway crosses the Chagres upon the bridge resting on a vertical
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 18-4 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. Station is reached, where the stream of the same name has cut down through the clays to a black rock similar to that of Bujio. At Tavernilla Station (Colon miles) the Canal Company has cut into a small hill apparently composed of red clay. At its base is the first undoubted exposure of a peculiar rock which may be called tem- porarily the Barbacoas formation. At Barbacoas (Colon 23 miles) the railway crosses the Chagres upon the bridge resting on a vertical bluff of some 30 feet in height. Rising above the track is a hill some 40 feet or more, making in all an expos- ure of some 70 feet of the rocks which dip slightly northward towards the Caribbean Figure 6. Section across Chagres River at Barbacoas. The first sight of this bluff created the impression of a stratified chalky limestone, but closer examination showed it to consist of a loosely cemented, white earthy rock, composed of firm fine particles, apparently siliceous, but water sorted, and showing distinct lines of lamination, in alternating degrees of fineness and coarseness. Throughout the mass were numerous white specks of a softer material, which seemed to be the small rounded decomposing pebbles of rhyolite. Macroscopically this earth strongly resembled the Radiolarian beds of Cuba, and the volcanic glass deposits of the Great Plains region of the United States. I was also fortunate in finding the basement relations of the Barba- coas beds at the village of San Pablo, half a mile to the west of Bar- bacoas. About 100 yards west of the station of San Pablo the white Barbacoas formation grades down into a mass of brownish rock, studded with fragments of decomposed light blue eruptive pieces embedded in it. It has an earthy texture and is easily cut with a hammer. It is of light specific gravity, and apparently a long decomposed conglomerate of vol- canic material
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Keywords: ., bookauthorha, bookcentury1800, bookdecade1860, booksubjectzoology
