VOLCANIC NAPHTHA SPRINGS. 193 



from Scinde to the mouth of the Persian Gulf, and are most numerous 

 in its eastern portion. Their situation is remarkable from the circum- 

 stance that, there are no traces of volcanic action on the coast. They 

 extend over 200 miles from Guadur to Kas-Kucheri, and vary in 

 height above the plain from 20 feet to 400 feet ; they are truncated 

 at the top, and have circular craters, in some cases 100 feet wide. 

 Here the mud is cold, somewhat thicker than treacle, and consolidates 

 into a compact substance. From time to time there is an ebullition 

 of gas. The mud ejected is chiefly clay, with some carbonate of lime 

 and a little quartz sand. Thus we remark a decline in temperature, 

 until there is no external indication of volcanic action, except the form 

 of the cone and its eruptive character. But there are other modes of 

 volcanic decline in which mechanically-suspended substances are never 

 brought to the surface, and the erupted matters are bituminous pro- 

 ducts or mineral and metallic matters in solution. 



Petroleum Springs. Asphalt is constantly met with in connection 

 with mud volcanoes. It may be sometimes absent (as when Hum- 

 boldt visited the cones of Turbaco, near Carthagena in JSTew Granada, 

 in 1801), and yet found plentifully fifty years later. In other dis- 

 tricts the discharge of asphalt or petroleum is permanent. Pallas 

 and other travellers have described the presence of bituminous 

 substances in the materials thrown out from the mud volcano of 

 Taman, in the Western Caucasus; but probably the best known 

 locality is Baku, 1 on the south side of the Caucasus, in the Caspian 

 Sea. Here the ground is so saturated with petroleum that it is 

 obtained by sinking wells ; and Eichwald has remarked that the 

 neighbouring cones should rather be called naphtha volcanoes than 

 mud volcanoes, since the outburst always ends with a large emission 

 of naphtha. Occasionally the naphtha, which floats on salt water, 

 takes fire during an eruption, and the flames rise to some height. In 

 the springs near Balachana the naphtha is derived from Upper Tertiary 

 sandstones ; but here, as in so many other localities, they exist in the 

 neighbourhood of volcanic rocks. In the Dead Sea, the asphalt has 

 been described by Lartet, and its appearance is associated with ther- 

 mal springs in a region of old volcanic action. 



In the island of Trinidad we see another phase of emission of 

 asphalt in the celebrated Pitch Lake, which covers an area of 99 acres, 

 and in the pitch banks which sometimes exist off the coast in that 

 island ; for here eruptive phenomena are entirely absent, except in a 

 few mud volcanoes scattered over the country. 2 



The origin of the bituminous matter is not easily accounted for. 

 Professor Ansted mentions a portion of a tree in the condition of 

 lignite obtained from one of the mud volcanoes of Northern Italy ; 

 and the constant association of these springs with districts of tertiary 



1 See Abich, "Mdmoires de 1'Academie, Imp. St. Pdtersbourg," viii. Se"rie, tome 

 vi., No. 5. 1863. Trautschold, Ueber die Naphtaquellen von Baku, ' ' Zeitschrif t 

 der Deutschen G^olog. Gesellschaft," xxvi. Bd. p. 257. 1874. 



2 See Wall, Geol. Survey, Trinidad, where a belief is expressed that the mineral 

 pitch is formed on the surface, out of existing vegetation. 



VOL. I. N 



