1906.] 



SEE— THE CAUSE OF EARTHQUAKES. 375 



still part of the fluid lava. The presence of minutely cellular fragments is 

 characteristic of most volcanic fragmental rocks, and this structure may 

 commonly be observed in the microscopic fragments and filaments of glass. 

 A characteristic feature of these minute fragments is the frequent occur- 

 rence among them of semi-circular or elliptical (' hour-glass ') shapes, which 

 evidently represent the sides of vesicles or pores that enclosed vapour or 

 gas in the molten rock, and were disrupted and blown out during volcanic 

 explosions." 



§ 45. On the supposed absence of volcanoes in the Alps and 

 Himalayas, and on the former existence of these vents in the interior 

 of continents. 



It is frequently remarked that volcanoes do not appear in the 

 Alps and Himalayas, and the inference has been drawn that no 

 volcanoes originated in the formation of these great mountain 

 ranges. But it is well known that at some time in the past geological 

 ages volcanoes existed in almost every part of every country, and 

 mountain chains like the Alps and Himalayas are no exceptions to 

 the general rule. Professor Suess (" Face of the Earth," Vol. I, 

 pp. 201-274) mentions some volcanoes formerly active in the Alps, 

 and undoubtedly similar vents once existed in the Himalayas. In 

 the course of time nearly all surface trace of eruptions is lost 

 where the glaciation, denudation and sedimentation are active, as in 

 the Himalayas. When we consider how imperfect our knowledge 

 of those mountains is, not only because they are high, but also 

 inaccessible to exploration, the failure up to this time to find extinct 

 volcanoes or their products is not remarkable. Craters are soon 

 covered by ice and worn down by the grinding action of glaciers, 

 while their ashes and lavas are equally covered and lost from view. 



Major Button justly remarks that the regions which have been 

 exempt from volcanoes are small in comparison with those which 

 have had them; and he observes that going back to early Tertiary 

 times we find them occurring where they have long been extinct. 



" The grandest volcanic field in the world was central and southern India 

 in Cretaceous times, when there was not a volcano in all Europe, and ex- 

 tremely few in North and South America. In the Jura-Trias, the Appa- 

 lachian region, from Labrador to the Gulf of Mexico, bristled with them, 

 and vast plateaux of lava were outpoured. In Paleozoic, they abounded in 

 the region of the Great Lakes, in Missouri, in Arkansas, and in eastern Texas. 

 There is hardly a county or bailiwick on the whole mundane sphere which 

 has not had its volcanic cycle at some time or other, and there are many 



PROC. AMER. PHIL. SOC, XLV. 184 X, PRINTED FEBRUARY 25, I907. 



