34 o SCIENCE PROGRESS 



sufficient to establish so important a conclusion, but fortunately 

 it does not stand alone. The Hotting breccia is fossiliferous, 

 and has yielded a number of leaves and other remains of plants : 

 these fossils are indeed fairly common, and the visitor who 

 should fail to find at least a few examples would be singularly 

 unfortunate. No less than forty-two species have been identi- 

 fied ; they include among others the fir (Pinus sylvestris), spruce 

 (Picca sp.), maple {Acer pseudo-platanus), buckthorn {Rhamnus 

 franguld), several willows {Salix nigricans, S. glabra, S. incana, 

 S. triandra), the wayfaring tree {Viburnum lantana), yew {Taxus 

 baccata), elm {Ulmus campestris), strawberry {Fragaria vcsca), 

 self-heal {Prune/la vulgaris), beech {Fagus silvatica), and mountain 

 ash (Sorbus aucuparia). None of these or of any of the re- 

 maining species are of distinctly boreal or alpine type. 



Three of the most important plants we have reserved for 

 special mention : they are a new species of buckthorn, Rhamnus 

 Hoettingcnsis, related most closely to R. latifolia, now living in 

 the Canary Isles, the box {Buxus sempervirens), also a southern 

 species ; and most important of all a Rhododendron (R. 

 ponticum), which now lives in the Caucasus, five degrees south 

 of the latitude of Innsbruck, and in a climate on the average 

 3° C. warmer. Taking all the facts into consideration Penck 

 concludes that the climate of Innsbruck in the days of the 

 Hotting breccia was 2° C. higher than it is now : in corre- 

 spondence with this the snow-line stood 1,000 ft. above its 

 present level, and the Alps, save for the higher peaks, were 

 almost completely denuded of ice and snow. 



The region round Hotting thus furnishes us with evidence 

 of revolutions of climate on the grandest scale ; the lower 

 boulder cla)^ representing the third glacial age, witnesses to 

 a time when the snow-line of the Alps had descended 4,000 ft. 

 below its existing level, and the valley of the Inn was filled 

 with ice ; the Hotting breccia, representing the third genial 

 age, equally testifies to a time when the ice had disappeared 

 and the mountains had been relieved of their mantle of snow, 

 when also a varied forest growth, thickets of the pontic 

 Rhododendron, and a multitude of flowering annuals covered 

 the bare rocks, and adorned the dreary expanses of boulder 

 clay ; the upper boulder clay, representing the fourth and last 

 glacial age, witnesses to a final advance of the ice, when the 

 snow-line again crept down to its previous level, 5,000 ft. below 



