HILL: GEOLOGY OF THE ISTHMUS OF PANAMA. 237 



Coal in the Isthmian Tertiary. — The older Tertiary sediments of the 

 Isthmian region are characterized by lignite. The presence of these 

 coals in extensive beds is strong evidence of the close proximity of large 

 land areas during the epoch of their deposition. 



While at Colon, Colonel Rives, Superintendent of the Railway, 

 informed me of several coal deposits to the north of the road, especially 

 one of unusual interest on the Rio Indios, a confluent of the Chagres, 

 rising along the divide north of the town of Chorera. Commander Lull's 

 Report 1 gives all the known geological information concerning these 

 localities. 



Still westward on the Isthmian region the coal bearing sandy clays 

 have great development around the Chiriqui Lagoon, where they 

 were studied in the year 1857, by Dr. John Evans. In his report 

 he says : " On microscopic examination of their fragments and of the 

 ashes of the coal when burnt, the structure of cellular plants which 

 formed it is discerned quite distinetly. The fossil plants, leaves, etc., 

 associated with the coal, were endogenous and allied to or identical with 

 those at present growing in the vicinity." Later these shells were studied 

 by Dr. C. T. Jackson, 2 who stated that, judging from the fossils, such as 

 Cardum, Cerethium, Natica, Mytilus, and other shells, this coal belongs 

 to the Upper Eocene Period. They were also studied by Gabb, 3 who 

 referred them to the " Miocene," which is the Oligocene of this paper. 

 The fossil shells are all Eocene or Miocene Tertiary (salt water shells) ; 

 none older were discovered in the coal formations. 



The observations of Gabb in the eastern lying province of Talamanca, 

 and of Sapper in Guatemala and Chiapas, show that these lignites are 

 a marked characteristic of the Tertiary formations of the Caribbean 

 coast westward of Colon. They also continue eastward of Colon around 

 the Colombian coast. 



Maack frequently mentions these lignite deposits, 4 and considers them 

 to " belong to the Tertiary formation mentioned above." 



From these notes it is seen that coal bearing clays have an extensive 

 distribution over the whole Isthmian region and the Caribbean coast of 



1 A description of the Rio Indios coal mines is given on pages 30-33 of the 

 " Reports of Explorations and Surveys for the Location of Inter-oceanic Ship Canals 

 through the Isthmus of Panama, and by the Valley of the River Napipi, by U. S. 

 Naval Expeditions, 1875, Commander Edward P. Lull, U. S. N., commanding 

 Panama Expedition." Washington, D. C, 1879. 



2 Proc. Bost. Soc. Nat. Hist., Vol. VII. p. 423, 428, 1861. 



3 Proc. Acad. Nat. Sci. Phila., Vol. XII. pp. 567, 1860. 

 * Harper's Magazine, 1873, Vol. XL VII. p. 805. 



