DOMAIN II. SILICEOUS. 



ingenious system of mineralogy. In like man- 

 ner rocks now universally admitted to consist of 

 granular quartz, or that substance crystallised 

 in the form of sand, were formerly supposed to 

 consist of sand agglutinated. Several primitive 

 rocks contain glands of the same substance, and 

 that great observer, Saussure, has called them 

 Glandulites, an useful denomination, when the 

 glands are of the same substance with the rock ; 

 while Amygdalites are those rocks which con- 

 tain kernels of quite a different nature. He 

 observes, that in such a rock a central point of 

 crystallisation may attract the circumjacent 

 matter into a round or oval form, perfectly de- 

 fined and distinct; while other parts of the sub- 

 stance, having no point of attraction, may co- 

 alesce into a mass. The agency of iron may 

 also be suspected, that metal, as appears from 

 its ores, often occurring in detached round and 

 oval forms of many sizes, and even a small pro- 

 portion having a great power*. 



On the other hand, many kinds of pudding- 

 stone consist merely of rounded pebbles. Saus- 

 sure describes the Rigiberg, near the lake of 

 Lucerne, a mountain not less than 5800 feet in 



* Buffon had on his estate a large and important mine, in which 

 the iron ore was solely in the form of peas. 



