IN THE SOUTH ISLAND OF NEW ZEALAND, ETC. Ill 
Mr. Fox’s observations on the damming-up of valleys by glacial 
and other detritus also go to confirm what I have observed and 
written in former years (see A. Irving, on “ The Origin of Valley- 
Lakes,” Quart. Jour. Geol. Society , loc. supra cit., supplemented by a 
summary of Heim’s monograph on “ Bergsturze,” Geol. Mag., March, 
1883). Two marked instances of this, from my own Alpine obser- 
vations, may here be cited : (i) that of the Rosegg in the Engadine, 
where the retreating glacier at the head of the Rosegg Thai has left 
exposed the gravel-strewn bed of the quondam intra -morainic lake, as 
the overflow of that lake has sawn its way down, so as to cut a 
gorge of 300 to 400 feet deep through the terminal moraine, since 
Quaternary times ; (ii) the case of the Achensee in the Tyrol, where 
the present lake occupies a faulted valley to a depth of over 2,000 
feet, the drainage having been reversed during the Quaternary 
Period, by the damming-up with glacial detritus of the ancient 
valley at Maurach, cutting off the waters from the Gorge of Jenbach 
and the Innthal, and diverting their flow to the north by the 
Achenthal into the Isar. Such damming-up on a grand scale was 
described years ago by Professor J. W. Spencer, as the origin of the 
Niagara overflow from Lake Erie, and was known to the German 
geologists as the true cause of the overflow of the Bodensee at the 
Falls of Schaff hausen. 
In the face of such evidence and of further facts and reasonings 
contained in my paper, “On the Work of Glaciers,” which 
appeared in Natural Science some sixteen years ago, one may be 
justified in accepting Mr. Fox’s conclusions as sound to Science, and 
in demurring to the proposition, that the late Sir Andrew Ramsay’s 
theory “ has not been seriously undermined,” as has been recently 
asserted in a paper entitled “ Ice or Water 1 ” read before the 
Victoria Institute last year. 
