394 NOTES ON THE GEOLOGY 



thence to Baiboot; and thence to Trebizond. I shall reverse 

 this order in giving an account of the specimens. 



An examination of the specimens and the statements of Mr. 

 Perkins, cstuljlishes the fact, that limestone is the prevailing rock 

 on this route ; forming even the high mountain chains that are 

 crossed. The greater part of it is a dull compact rock, which I 

 suspect to be older than tlie cretaceous formation of Egypt and 

 Palestine, chiefly because Prof. Bailey could detect in none of 

 the specimens Polythalamian remains, like those of the chalk, or 

 indeed any others. Occasionally, the specimens are chalky and 

 marly, like those from Palestine ; as No. 426, from Hassan Aillah 

 and Erzeroum, and No. 445 from Baiboot. In short, I cannot 

 doubt that nearly all the specimens belong to the fossiliferous 

 rocks, and probably to the older varieties. Mr. Perkins also says, 

 that while most of " the ranges of mountains between Trebizond 

 and Erzeroum are soft limestone, here and there a naked gi-anite 

 peak peers above the general surface in sublime sterility." He 

 did not, however, bring along any specimens of this granite. 



It will be perceived, that the route of Mr. Perkins crosses, to- 

 ward its eastern part, that broad tract of country, which, extend- 

 ing from the Azore Islands to the Caspian Sea, exhibits many 

 traces of recent and extinct volcanic action. We see the evi- 

 dence of this in many of the specimens, and in the mineral 

 springs, some of them thermal, that occur in abundance. 



The specimens No. 472, 473, of the rocks usually employed 

 for purposes of construction in Trebizond, appear to be trachyte, 

 with imbedded crystals of hornblende, though they approach 

 certain aggregates sometimes found with the primary rocks. 

 Another evidence of the igneous origin of the rocks around that 

 city, presents itself in specimens No. 489 to 493, picked up 

 on the shore of the Black Sea at that place. They consist of 

 chalcedony, carnelian, agate, amygdaloid, &:c., which must have 

 come from rocks of igneous origin. No. 425 is another curious 

 illustration of the same fact. For, if I mistake not, it is almost 

 entu-ely composed of gi-ains of olivine, a mineral alnmdant in 

 basalt and lava. The rock containing it must be in large quan- 

 tity somewhere in the vicinity, to produce enough to be gathered 

 as sand upon the shore, 



