426 REACTION OF THE INTERIOR OF THE EARTH 



case in the last century, when the whole morphology of 

 volcanoes was limited to cones and domes or bell-shaped 

 mountains. We are now most satisfactorily acquainted 

 with the structure, hypsometry, and arrangement (with 

 what the ingenious Carl Friedrich Naumann calls the 

 " geotektonik ") ( 588 ) of many volcanoes, while we are 

 still in great uncertainty respecting the composition of 

 their rocks, and respecting the association of mineral 

 species which characterise their trachytes, and can be 

 recognised apart from the ground mass. Both these 

 kinds of knowledge, however, the " morphologi- 

 cal" for the rocky frameworks, and the "oryctognos- 

 tical" for their composition, are alike necessary for 

 forming a complete judgment in respect to volcanic acti- 

 vity; indeed, the latter kind, based on crystallisation 

 and chemical analysis, may be regarded as the more 

 geologically important of the two, on account of the 

 connection with plutonic rocks (quartzose-porphyry, 

 greenstone, and serpentine). All the little which we 

 suppose we know of what we call volcanic character in 

 the moon is, from the nature of the case, restricted 

 solely to form. ( 589 ) 



If, as I hope, any interest attaches to what I have 

 here said respecting the classification of volcanic rocks, 

 or rather respecting the division of trachytes according 

 to their composition, the merit of the grouping belongs 

 entirely to my friend and Siberian travelling compa- 

 nion, Gustav Kose. By his own observations in the 

 open field over extensive regions, and by a happy com- 

 bination of knowledge in chemistry, crystallographic 

 mineralogy, and geology, he has been peculiarly well 

 qualified for promulgating new views respecting the 



