334 SUMMARY OF THE CONTENTS OF VOL. II. 



nolia, Helianthus annuus, Victoria regina, Euryale amazonica, 

 &c. , 203, 240 



The different forms of plants determine the character of the landscape 

 as dependent on vegetation in different zones. Physiognomic 

 classification or division into groups according to external " facies" 

 or aspect, entirely different in its principles from the classification 

 according to the system of natural families. The study of the 

 physiognomy of plants is based principally on what are called the 

 vegetative organs, or those on which the preservation of the 

 individual depends ; systematic botany grounds the arrangement 

 of natural families on a consideration of the reproductive organs, 

 or those on which the preservation of the species depends 205 210 



On the Structure and Mode of Action of Volcanos in the different Parts 

 of the Earth- -p. 211 to p. 241. 



Influence of journeys in distant countries on the generalisation of 

 ideas, and the progress of physical geology. Influence of the 

 form of the Mediterranean on the earliest ideas respecting volcanic 

 phenomena. Comparative geology of volcanos. Periodical recur- 

 rence of certain natural changes or revolutions which have their 

 origin in the interior of the globe. Relative proportion of the 

 height of volcanos to that of their cones of ashes in Pichincha, 

 the Peak of Teneriffe, and Vesuvius. Changes in the height of 

 the summit of volcanos. Measurements of the height of the 

 margins of the crater of Vesuvius from 1773 to 1822 : the author's 

 measurements comprise the period from 1805 to 1822, 213228 



Particular description of the eruption in the night of 23-24 

 October, 1822. Falling in of a cone of cinders 426 English feet in 

 height, which previously stood in the interior of the crater. The 

 eruption of ashes from the 24th to the 28th of October is the most 



