446 GEOLOGY. 



of Germany. The aggregate thickness of the igneous rocks is, in 

 Scotland, as much as 6000 feet, and the rocks are, in places at least, 

 regularly interbedded with the sedimentary series. The eruptions 

 seem to have been in part subaqueous, and in some cases so consider- 

 able as to build up the sea- or lake-bottom until it became land. As 

 the result of the great erosion which has since taken place, the igneous 

 rocks now form considerable ranges of hills (Pentland, Ochil, etc.). 

 There are thousands of feet of sedimentary rocks without volcanic 

 beds associated, both above and below the volcanic portions. 



The upper division of the Old Red sandstone formation is not so 

 thick as the lower. The unconformity between it and the lower division 

 is a great one, and shows that changes of relations were taking place 

 on a considerable scale. The bodies of water appear to have been 

 shifted somewhat in position from time to time so that the formations 

 made in one place at one time were exposed to prolonged erosion before 

 they were again submerged and buried by younger strata. 



In the upper division of the Old Red sandstone of Great Britain 

 there are conglomerates of such a character as to have raised a question 

 concerning the existence of glaciers in this region in Devonian times. 

 The conglomerates contain bowlders of all sizes, up to eight feet in 

 diameter. While the smaller stones are usually well worn, the larger 

 ones are often distinctly subangular. All sorts of durable rock are 

 represented. The large bowlders seem not to have come in from dis- 

 tant regions, but some of the smaller stones may have come from 

 greater distances, since no local source for them is known. Further- 

 more, some of the bowlders are said to be striated, and it is believed 

 by some geologists at least that the striae are glacial. The matrix of 

 the conglomerate is in keeping with the hypothesis that ice cooper- 

 ated in its making. It has been suggested 1 that the Highlands of 

 Scotland were then much higher than now, that they harbored glaciers, 

 and that the bergs to which the glaciers gave origin made, or helped 

 to make, the conglomerates here referred to. The conglomerate is 

 to be seen in the Lammermuir Hills, and in the Silurian hills of Cum- 

 berland and Westmoreland, in northern England. 



Fossils of the " Old Red " type have been found within the Arctic 

 circle on Bear Island (lat. 70° 30' N.), between the coasts of Norway 



1 Neumayr, Erdegeschichte, Vol. II, p. 133. 



