PREFACE. 
In the summer of 1 86 1 I had the pleasure of 
spending a short holiday in Switzerland with Huxley 
and Tyndall. Tyndall and I ascended the Galen- 
stock, and started with Benen, who afterwards lost 
his life on the Haut de Cry, up the Jungfrau, but 
were stopped by an accident to one of our porters, 
who fell into a deep crevasse, from which we had 
some difficulty in extricating him, as Tyndall has 
graphically described in his Hours of Exercise on the 
Alps. 
From that day to this many of my holidays 
have been spent in the Alps. On them I have en- 
joyed many and many delightful days; to them I 
