Prof. T. G. Bonney—Rounding of Alpine Pebbles. 59 
they receive some sub-Alpine tributaries. Consequently, limestone 
pebbles characterize their gravels. 
Besides these observations we repeatedly had indications of the 
gravel of the great plain, either from the stones scattered over the 
fields, from ballast pits, or from railway cuttings. Here also 
pebbles often about 3 ins. or 4 ins. are common, with occasional larger 
ones. In fact, they frequently are very similar in size to those of the 
Bunter Conglomerate in Staffordshire, but generally not quite so 
well rounded. Limestone becomes more common, as might be 
expected, as we proceed eastwards. This remark holds, I believe, 
of the great plain of Lombardy as far as the south end of the Lake 
of Garda. 
Old drifts, repeatedly seen between Lyons and Grenoble, in size, 
amount of rolling and arrangement, bore a remarkable resemblance 
to the Bunter pebble-beds of Staffordshire (except that the materials 
were mainly limestone). This was particularly the case near Virencal, 
where the section was some 40 feet high, and the pebbles were parted 
by streaks or bands of sand. The old drifts of the Rhine at Stein 
and near Bale are very similar. 
In regard to the Lake of Garda, I endeavoured to ascertain the 
action of its waves on the beach pebbles. These are abundant to 
the east of Desenzano, and they have evidently been derived from 
the north. They are fairly well rounded, but seeing that similar 
pebbles, about as well rounded, occur in the drifts of which its banks 
consist, no inference can be drawn from them. But I observed that 
well-rounded pebbles had been formed on the shore from fragments 
of a soft red brick; also that shards of ordinary red earthenware 
had been sometimes fairly well rounded. It must be remembered 
‘that the Lago di Garda is noted of old for its waves, ‘“fluctibus et 
fremitu assurgens, Benace, marino;” but, as a rule, the great sub- 
Alpine lakes have not, so far as I have noticed, much effect on rock 
fragments. 
It is difficult to give precise statements of the amount of fall in 
the Alpine rivers; but the following are rough approximations, 
calculated from the heights quoted in guide-books, which of course 
do not give the exact level of the river at the place, and from the 
distances by road, which, at any rate when the valley is tolerably 
level, are generally rather sometimes considerably shorter than the 
river course. : 
The Inn, from St. Moritz to Samaden (three miles) falls about 
65°3 feet per mile; from Samaden to Landeck (794 miles) about 
37°3 feet per mile; from Landeck to Innsbruck (52% miles) about 
13-8 feet per mile; from Innsbruck to Jenbach (23 miles) 3°83 feet 
per mile (I believe rather more, for I think the height given for 
Jenbach is above the Inn—possibly 80 or 100 feet too great). 
The Ziller from Ginzling to Mairhofen (about 73 miles) falls 
155-5 feet per mile; from Mairhofen to Zell (44 miles) 17-8 feet per 
mile; from Zell to Jenbach about 4:6 feet ora little more (this, for the 
above reason, and as the embouchure of the Ziller is not at Jenbach 
itself, is a very rough estimate). 
