248 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



When at length the running survey of the mountainous portion of 

 the frontier was proceeded with, it advanced with such rapidity that 

 the party was seldom two days encamped upon the same spot ; thus 

 there occurred no opportunities for minute geological investigation. 



Other difficulties of no ordinary nature presented themselves. Our 

 route lay through the midst of those wild mountain tribes who from 

 time immemorial have never acknowledged law or subjection, and 

 who regarded our movements with infinite distrust. Owing to the 

 insecurity of the coimtry, habitations were so few that we were fre- 

 quently obliged to carry provisions for many days together. Add to 

 these facts the ruggedness and inaccessibility of the passes and 

 mountains, as well as the intense heat of the climate (sometimes 

 reaching 1 24° Fahr. in the shade), and it may be conceived that our 

 labours were attended with considerable danger as well as difficulty. 

 Under these circumstances, I trust that every allowance will be made 

 for the imperfect nature of this communication. 



In this place I cannot omit returning my sincere thanks to Her 

 Britannic Majesty's Commissioner, Lieut. -Col. Williams, C.B., for 

 the facilities he invariably afforded me, and without which it would 

 have been utterly impossible to have reached such localities as I con- 

 sidered desirable for the prosecution of my researches. 



Mr. Ainsworth is the only geological author who has, from actual 

 observation, written on the structure of any portion of the country 

 under consideration ; and, although I had no opportunity of going 

 over the same ground, his ' Researches in Assyria, Babylonia, and 

 Chaldaea,' in connexion with the labours of the Euphrates Expedi- 

 tion, have been of considerable aid to me in tracing the geographical 

 extent of the various formations in their western range. 



The line of country investigated during the survey bears in a 

 N.N.W. direction from Mohammerah, at the head of the Persian 

 Gulf (lat. 30° 26' N.), to Mount Ararat (lat. 39° 42' N.) ; a direct 

 distance of rather more than 600 geographical miles. See Map, 

 PI. IX. 



The first 250 miles, from Mohammerah to near Mendali, is an 

 arid and deserted waste, infested by plundering parties of Arabs and 

 Kurds, but capable for the most part of extensive cultivation. 



From Mendali to Zohab (50 miles) the exterior Tertiary chain of 

 low gypsiferous ridges, which everywhere skirt the west flank of the 

 Zagros, is crossed ; and at the latter place the Nummulitic limestone 

 and Cretaceous rocks are first reached. See General Section*, fig. 1. 



From this point to near the Lake of Zerribar (60 miles) is a suc- 

 cession of regular saddle-shaped limestone anticlinals, with alternate 

 synclinals containing disconnected portions of the gypsum-series, and 

 underlaid by older blue schists. 



The remainder of the Frontier exhibits a lofty range, composed of 

 igneous rocks, which, bursting through the stratified deposits, con- 

 stitute the axis of the vast barrier-ridge nearly as far as Bayazid at 

 the southern foot of Mount Ararat, a distance of 270 miles. 



* The woodcut diagrams, reduced from the original sections, are to be found 

 at pp. 326-344. 



