Mr. Horner on the Mineralogy of the Malvern Hills. 285 



size of a walnut, the surfaces of which are generally covered with 

 oxide of iron, probably arising from a partial decomposition. This 

 is the case, not merely near the surface, but in some degree even 

 where the rock has been quarried to a considerable depth. This 

 peculiarity renders it very difBcult to obtain such a fracture as shews 

 the real nature of the rock, and makes it almost impossible to pro- 

 cure good cabinet specimens. 



§ 9. When I first began to examine the rocks of which these hills 

 are composed, I v/as particularly struck with the great variety that 

 presented itself, for almost every specimen which I detached within a 

 very limited space, offered a new character. A closer examination, 

 however, shewed that there is a greater uniformity than I at first sus- 

 pected, and that the diversity of appearance depends on the different 

 proportions in which the same materials are united together. Fel- 

 spar, hornblende, quartz, and mica, forming different compound 

 rocks, and varying as much in the size as in the proportions of the 

 ingredients, constitute the greater part of the range. There are very 

 few rocks in which the size of the component parts is so minute as 

 to give the internal structure a homogeneous appearance. 



§ 10. If every " compound granular aggregated rock, composed of 

 felspar, quartz, and mica," is to be considered as granite, a very great 

 part of the Malvern hills is composed of it ; but among the various 

 compounds of that nature, found in this place, there are very few 

 which present the same appearance as the granite of Alpine countries ; 

 they have not the decided crystalline structure, which these granites 

 usually exhibit ; nor are the several parts so closely intermixed. The 

 felspar is generally red, and predominates considerably in the mass ; 

 sometimes the quartz and sometimes the mica is wanting, but more 



