INTRODUCTION. 



upon these two kingdoms have hence been enabled to glean 



the most interesting topics, and to form general compilations 



of great merit and accuracy. For as vita brevis, ars longa, 



was the axiom of Hippocrates, who compiled his classical pro- 



ductions on medicine from cases preserved in the temples, so 



in all the other sciences, the mere observations of one man ^ 



will not constitute a science or a system. Saussure passed 



forty years amongst the Alps ; and if the years consumed by 



other travellers and authors, whose works have been used in 



the present compilation, were computed, they might amount 



to a thousand ; a period belonging to nature and science, 



but not to man. Hence the utility of general systems or Utility of 



compilations, which, by combining in one view the observa- com pi j ations. 



tions of practical or scientific predecessors, not only by colla- 



tion and elision render them more intelligible, but ascertain 



the progress attained by any science 5 so that future diligence 



may not be wasted in the investigation of subjects already 



illustrated, but be directed to such parts as remain unculti- 



vated and obscure. In this also, as in the other sciences, 



more genius is required to build a system, than to make 



observations. In the latter, Newton must yield to Herschel. 



As the study of mineralogy commenced upon principles Petralogy dif- 

 afterwards found to be inadequate and erroneous; so, by a fersfrom 

 similar fatality, the study of rocks has been confounded with 

 what is called geology, or the doctrine of the constitution of 

 this globe, which rather belongs to natural philosophy. 

 Petralogy, like lithology, or metallogy, is a science which 

 must be studied by the geologist ; but a theory of the earth 

 may as well be studied in a pebble, as in a rock $ and the 

 neglected plains, as being nearer the centre of the earth, 

 must afford more topics than the lofty rocks and the moun- 

 tains. There is no reason, therefore, particularly to connect 

 petralogy with geology, or what some call geognosy : and it 

 would be alike absurd and useless if a rock could not be 

 classed, without a dissertation to determine its antiquity. 

 Nor can any reason be perceived why Werner should regard 



