OF VOLCANIC ROCKS. 9] 
occur. The Alps and the Himalaya are the most striking instances of this kind. The 
first of these, and probably, too, the other, had, as we mentioned before, undergone a 
considerable elevation in and after the porphyritic era, but have probably changed their 
altitude very little in the next following periods. The acceleration of their elevation 
during the voleanie era appears, however, to have greatly exceeded that of the Andes. 
The coincidence in time of these events, and of all the phenomena characteristic of the 
volcanic era, justifies the supposition that they are connected in their origin. 
’ If we contemplate, in its relations to the volcanic era, the great elevated belt of 
which the Alps and Himalaya form the axis, we find it to consist of three parallel 
zones. ‘The central one comprises those two mountain ranges and the broad moun- 
tainous country which connects them, and which owes its configuration chiefly to the 
events of the volcanic era. The Alps and Himalaya are free from volcanic rocks. This 
is also true as regards the central portions of those chains which branch off from the 
Alps in a southeasterly direction, and of those (as far as their geology has been ex- 
plored) which extend westerly from the Himalaya. The farther one proceeds in the 
Turkish peninsula towards the east, the more frequent are the monuments of eruptive 
activity of the volcanic era; they are known in Servia and Bulgaria, in the north, and 
in Macedonia, Thracia and Epirus, in the south. They increase in similar ratio as 
one proceeds westerly from the Himalaya, through the highlands of Armenia to Asia 
Minor. If it is considered that active volcanoes are particularly numerous in those 
regions where the elongated portions of two different continents have, as it were, a 
tendency to connection, the analogy with the mode of distribution of volcanic rocks 
in the regions mentioned is conspicuous. The system of the Alps with its southeastern, 
and that of the Himalaya with its western branches, were disconnected before the Ter- 
tiary period, and were united into one mountainous belt during the same. The eruptive 
activity contemporaneous with this slow process was remote from the main axis where 
this had existed as an elevated range before, and approached it more and more, from 
both sides, increasing, at the same time, in intensity, until it culminated in that 
region where the connection of both systems was effected. Massive eruptions and 
voleanic activity have ceased completely in this central zone. 
North of this, is another zone, which was distinguished in its entire length by 
the intensity of eruptive action in the volcanic era. It stretches from Central Asia by 
the Caspian Sea, the Caucasus, the Crimea, the Carpathians and, in branches, through 
central Germany to central France. In the European portion of this zone, there are 
only recognizable in thermal and mineral springs the last feeble remnants of former 
volcanic activity, while they are somewhat more energetic in that portion which is 
situated on the Asiatic continent. A third zone, not less distinguished for the in- 
tensity of eruptive action in the volcanic era, accompanies the main axis to the south. 
It traverses India, and, in the Bay of Bengal, is connected with the volcanic belts of the 
Indian Archipelago, while it continues to the west through Arabia, Syria, Palestine, to 
the Mediterranean, where it comprises the active voleanoes of the Grecian Archipelago 
and Italy, and is connected by Sardinia and southern Spain with the Azores. Volcanic 
activity still continues in this belt, but the period of the massive eruptions has passed 
long ago. 
(129) 
