THE ISTHMUS OF PANAMA. 39 



Col. Hughes, in his report, says that the two con- 

 tinents, as they formerly existed, are now connected 

 by a series of uplifted hills of variable height, form- 

 ing a not well defined, but sinuous and contorted 

 ridge, dividing the waters of the Pacific from those 

 of the Atlantic, curving through the Isthmus of Pan- 

 ama in the form of an arc. Upon the slopes of this 

 ridge, and often towering above it, are seen isolated 

 conical hills, sometimes connected with each other, 

 or with the dividing range, by low ridges of land. 

 Nearly the whole of this formation is obviously re- 

 cent, and of igneous origin. It consists of porphyry, 

 greenstone, columnar basalt, hornblende, and tra- 

 pean rocks ; and altered Jimestone and granites, 

 changed from other rocks by the action of fire, also 

 occur. A considerable variety of minerals are found, 

 such as copper and iron, agates, chalcedonies, and 

 cornelians ; and gold has been discovered in almost 

 every stream, especially on the Atlantic slope ; in- 

 deed it is not improbable, from the many indications 

 of its existence, that the mines of this metal may 

 prove, on further examination of the country, to be 

 of great value. Where sedimentary rocks are found, 

 it is obvious that they are of still more recent origin 

 than the igneous formations, and have been deposited 

 since the upheaving of the latter, as they abut upon 

 tli em, without disturbance of their strata, which are 

 perfectly horizontal. Some exceptions to this rule 

 are mentioned, but they escaped the observation of 

 Colonel Hughes. It is almost impossible to resist the 



