264 SCIENCE PROGRESS 



paper; moreover, that it is on the lines along which petrology 

 has been advancing during the past two decades, and possesses 

 a very great advantage in retaining, for its chief families, names 

 that are in general use in the languages of all countries where 

 petrology is studied, without divorcing them from the signifi- 

 cance which they have acquired by custom or consent. 



