or Saussurite-smarag elite Gabbro of the Saasthal. 239 



laub side* of the flattened snow-saddle between the two glacier 

 basins. These knolls, as will presently be described, also 

 consist of a variety of gabbro. The ridge of which we speak 

 rises slightly from beneath the snow, and runs pretty nearly 

 on a level for about a couple of hundred yards, falling 

 steeply on either side towards the descending surface of the 

 glaciers. At the end, which falls no less steeply, it may be 

 200 feet above the icef. Mr. Eccles, in 1890, also found 

 gabbro in the above-named spur of the Allaleinhorn, but the 

 mass of it appeared to be small. I think these are all the 

 visible outcrops of any importance. That they are limited to 

 the vicinity of this peak is shown by the fact that we find the 

 erratics cease in the Saasthal as soon as we have got beyond 

 the right moraine of the Allalein glacier. We look for them 

 in vain over the stone- strewn bed of the valley above the 

 Mattmark See. 



Before describing the rock of these ridges it will be con- 

 venient to make some remarks on that of the boulders, where 

 really it is more conveniently examined, thousands of specimens 

 being, as it were, laid out for our inspection. There are many 

 varieties, some of which are much more numerous than others. 

 I noticed the following : — 



(1) A gabbro consisting mainly of felspar, varying from a 

 rather glassy bluish-white to white (that is to say, a somewhat 

 altered labradorite), and a brownish diallage, with lustre not 

 conspicuously metallic. Structure often ophitic. Varieties 

 occur from rather fine-grained to coarse, when the crystals 

 may be an inch or so long. Not common. 



(2) Specimens chiefly consisting of a greyish- white saus- 

 surite and a rather acicular hornblende of a dull slate-blue 

 colour, sometimes also containing pale-red garnet. Rare. 



(3) Specimens with but little of the pyroxenic constituent, 

 consisting mainly of saussurite and a pale reddish granular 

 mineral (garnet). Not very common. 



(4) A rock consisting of a white, rather granular, felspathic 

 mineral, and a rather fibrous hornblende, deeper and duller 

 in colour than the smaragdite and of a more actinolitic habit. 

 The two minerals occur generally in irregularly shaped 



* The latter is so small that it is omitted (necessarily) on the Swiss 

 map. 



t These were our estimates at the time. The Swiss map, if it is 

 intended to he strictly accurate, would add about 50 yards to the length. 

 Captain Marshall Hall states that he was three quarters of an hour 

 climbing up the end of the wall. Either he must haye found exceptional 

 difficulties or we have underestimated the height. 



S2 



