REVIEWS 283 
that the changes of relief which were effected during the interglacial stage in 
question were very much greater than those which have taken place since the 
outflow of the doleritic lavas. And yet these lavas have been glaciated more 
than once, and we do not know how long they had to wait for their first gla- 
ciation. 
We seem therefore justified in coming to the conclusion that the two gla- 
ciations in question have not been the result of comparatively insignificant 
oscillations of an ice-sheet, but were really separated by a protracted period. 
The very occurrence indeed of the interglacial streams of lava over such 
great areas suffices to show how extensively the ice-sheet melted away. It 
seems to me highly probable that @// the so-called “ preglacial”’ lavas are in 
reality interglacial. 
Furthermore, the evidence leads to the inference that the time which has 
elapsed since the last ice-sheet disappeared from the southern lowland of 
Iceland is very short as compared to the interglacial epoch that intervened 
between the first of the glaciations experienced by the dolerites and that next 
preceding it. 
Whether the supposed marine deposit which underlies the glaciated lava 
on Tungufljot dates back to the closing stages of the interglacial epoch just 
mentioned, or whether it ought rather to be ascribed to an interval separating 
the two glaciations which are represented by the two systems of striae upon 
the surfaces of the later dolerites, future investigations must be left to deter- 
mine. 
No doubt many additional conclusions are suggested by the observations 
recorded in this paper, but I do not care to consider these at present. As 
already stated, the chief object of this paper is to point out that there exists 
in Iceland much hitherto unsuspected evidence of former glacial action. I 
am indeed sanguine enough to think it not improbable that the records of the 
glacial period have been more fully preserved here than elsewhere. For it is 
obvious that the conditions for the protection and preservation of glacial 
deposits have been with us somewhat exceptional. While in other lands, 
free from volcanic activity, each succeeding ice-sheet has partly destroyed 
and partly covered up the deposits of its predecessor, in Iceland the moraines 
have been greatly sheltered by the products of volcanic eruptions which over- 
lie them. Moreover, crustal movements have contributed directly toward the 
same end by placing the old moraines beyond the reach, as it were, of suc- 
ceeding glacial invasions. Not improbably, too, some rocks of the “‘tuff- and 
breccia-formation”’ may be due to the direct interaction of volcanic and gla- 
cial forces. 
To this is added the discussion of some points of a more special 
and local nature. It is gratifying to learn that the investigation is 
likely to be continued. die (COGS 
