286 Mr. Horner on the M'lucrakgy of the Malvern Hills. 



frequently the latter. I shall, however, for the sake of brevity in the fol- 

 lowing descriptions, distinguish all those rocks, in the composition of 

 which these three ingredients are found, however disproportionate 

 they may be to each others by the general name of granite. I feel 

 the more warranted in doing so, from what [.Jr. Jameson has said in 

 the deiiniticn he gives of granite. " The parts," he says, " vary in 

 quantity, so that sometimes one, sometimes the other, and frequently 

 two of them, predominate. Felspar is generally the predominating, 

 as mica is the least considerable ingredient of the rock. In some 

 varieties the quartz is wanting ; in others the mica ; and these have 

 received particular names. Such distinctions, however, are useless." 

 But I considered it necessary to give this previous explanation of the 

 peculiarity of their structure, as the mere term granite would convey 

 to most mineralogists, an erroneous idea of the true nature of the 

 rocks I now allude to. I fhall also, for the sake of brevity, occasion- 

 ally distinguish those rocks in which hornblende forms a predomi- 

 nating ingredient by the general name of sienitic rocks. It would 

 be an endless task to give separate names to the various compounds 

 met with in the Malvern hills, although they certainly have different 

 external appearances ; and were 1 to attempt to do so, I should per- 

 haps be making distinctions, which their origin does not warrant, as 

 all the varieties comprehended in the same class have probably been 

 produced under similar circumstances. But in the present state of 

 geological science, and more especially when the great imperfection 

 of the nomenclature of rocks is considered, it would be well if geo- 

 logists made a practice of describing the simple minerals of which a 

 rock is composed, wherever they can be distinguished, instead of giv- 

 ing specific names without any explanation of the nature of the 



* Jameson's Geognosy, p: 102. 



