VOL. LXXXI.] PHILOSOPHICAL TRANSACTIONS. 11 



if both the basaltes and granite had been fluid together." Those specimens, 

 which show how copiously volcanos produce feldspath, shoerl, and mica, espe- 

 cially the 2 former (substances common both to basaltes and granite,) tend 

 greatly to establish the near relation between these 2 kinds of rock. Dr. B. was 

 surprized, at this day, to find an excellent observer seriously maintaining, that 

 these earthy crystallizations are merely ejected, and not generated, by these fires. 



Attempts have been made to set up boundaries between the columnar granite 

 of the Euganean hills, the granite of the volcanic provinces of France, the 

 granitello of the Italians, and such granite as is found to constitute high and ex- 

 tensive ranges of mountains. As to a difference in the size of particles, and 

 hardness of the stone, the first distinction is neither constant, nor by any means 

 calculated to persuade us that a cause, capable of producing the one, is inadequate 

 to the production of the other. It may probably be explained from the quantity 

 of matter, more or less perfect fusion, a different length of time in cooling ; and 

 in the latter character he suspects the observers to have been deceived by the de- 

 cay of the rocks they inspected. At all events, lavas in abundance show, that 

 fire is capable of producing any required degree of compactness. 



Dr. B. concludes this induction of particulars with an observation lately pub- 

 lished by one of our most intelligent mineralogical travellers. " Among the an- 

 cient black stones, the compound species are most frequent. They often consist 

 of a kind of granite, in which the scaly black shoerl predominates so much, that 

 the whole mass appears black. It is accompanied by white feldspath of so small 

 a grain, and so entangled among the shoerl, as to be sometimes scarcely dis- 

 tinguishable. The feldspath itself is sometimes transparent, and by transmitting 

 the colour of the shoerl, in which it is imbedded, appears black. Sometimes scales 

 of black mica occur. The constituent parts do not always observe the same pro- 

 portion ; and when the quantity of feldspath increases, the appearance of a real 

 grey or red granite is produced. Hence we have veins and spots of grey granite 

 in almost all the dark-coloured rocks that pass under the denomination of basaltes. 

 These veins have very much embarrassed those naturalists who maintain that all 

 basaltes has been produced by fire." This circumstance however, according to 

 Dr. B.'s view of the subject, is far from embarrassing : he considers it as a strong 

 proof of his opinion, since it seems to involve this consequence, that if basaltes 

 proceed from fusion, granite also must. Specimens, such as those here described, 

 he would place near granular basaltes, like that of Cape Fairhead. " In blocks 

 of ancient basaltes," proceeds M. Dolomieu, " I have observed the transition 

 from shoerl in a mass nearly homogeneous (I say, nearly homogeneous, because 

 I know of no stones, belonging, as these do, to the primitive mountains, with- 

 out indications of a separation of several substances which were incorporated to- 

 gether in a paste, or rather which are generated in that paste) to black and white 



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