TO NEAPOLIS. 15 
white colour in feldspar^ may perhaps always chap. 
be attributed to an incipient decomposition in v ■»» > 
the stone ; so great is its tendency to undergo an 
alteration of this nature upon being taken from 
its native quarry, in consequence of its alkaline 
constituent. Its loose fragments were all in such 
a state of decomposition, owing to this change in 
\he feldspar, that they crumbled, and were easily 
broken in our hands. Upon drawing nearer to 
the mountains upon the left, whence these frag- 
ments had been detached, we had the further 
satisfaction of discovering the same aggregate in 
its natural deposit ; the whole mountain appa- 
rently consisting of no other substance ^ In 
another hour and a half, coasting the borders 
(5) The author will take this opportunity to correct a very absurd 
error respecting the meaning of the ^otA feldspar, which has become 
prevalent, probably from the venerable Hauy having fallen into it 
himself. It is said to signify ''''field span" and thus Hauy (tom.ll. 
p. 25. " Feld-spath, c'est-k-dire, Spath des cha»ips") derives it 
from our cooimon English acceptation of the v/rrd field ; whereas it 
means mountain-spar; being a constituent of gianite, and therefore 
eaWedfeld-spnr, from the old northern or Danish word for a mountain, 
feld, or field ; as " Doire Feld," the highest mountain in Norway. 
(6) We brought from this place as many specimens as we could 
conveniently convey with us on horseback : some of them are now in 
the author's collection of minerals in the University of Cambridge, 
where they have been placed with the fragment of a large vase found 
at SaIs in Egypt, manufactured by the Antients of the same kind of 
porphyry. The quarries whence it was derived by antient lapidaries 
are entirely unknown. 
