ANNIVERSAKY ADDRESS OF THE PRESIDENT. 1 73 



Palseozoic ages in this country, we see clear evidence of a gradual 

 diminution in its vigour. The vridespread outpourings of lava and 

 tuff in the Silurian period in England, Wales, Scotland, and Ireland 

 were succeeded by the somewhat diminished, though still important, 

 eruptions of the Lower Old Eed Sandstone basins. The latter 

 were followed by the still lessened outflows of the Carboniferous 

 plateaux, which in turn preceded the yet feebler and more localized 

 eruptions of the Carboniferous puys, the whole prolonged volcanic 

 succession ending in the small scattered vents of the Permian period. 

 There were of course oscillations of relative energy during this history, 

 some of the maxima and minima being of considerable moment. 

 But though progress towards extinction was not regular and uniform, 

 it was a dominant feature of the i)henomena. 



6. The Permian volcanoes were the last of the long series, 

 and, so far as we yet know, the whole of Mesozoic time within 

 the area of Britain was absolutely unbroken by a single volcanic 

 eruption. The chronological value of this enormous interval of 

 quiescence may, perhaps, never be ascertainable, but the interval 

 must assuredly cover a large part of geological time. The next 

 eruptions were of older Tertiary date. They reproduced many of the 

 characteristic features of Palaeozoic vulcanism, and continued for a 

 long time, measured according to our notions of chronology, but are 

 not separable into clearly-defined periods like the Arenig and Bala 

 volcanic rocks in the Silurian system or the plateaux and puys 

 of the Carboniferous series. They form one great group which was 

 probably begun and completed in older Tertiary time. Since they 

 ceased, another interval of profound quiescence has succeeded, which 

 still continues. But this interval is almost certainly of less duration 

 than that which elapsed between the Palseozoic and Tertiary out- 

 bursts. In other words, remote as the date of those Tertiary volcanoes 

 appears to be from our own day, it comes much nearer to us than did 

 the era of the last Permian eruptions to the earliest of the Tertiary 

 series. 



7. Volcanic phenomena cannot be regarded as a mere isolated 

 and incidental feature in the physics of the globe. During the 

 short time within which man has been observing the operations of 

 existing volcanoes he has hardly yet had sufficient opportunity of 

 watching how far they can be correlated with other terrestrial 

 movements. Nor, when he endeavours to trace some such con- 

 nexion among the records of the geological past, has he yet collected 

 materials enough to furnish a sufficiently broad and firm basis of 



