3 8 Dr. Eajon on Cryjtallization. 
•where the pebbles are found, feem to have de¬ 
rived their origin from lava or volcanic matter.* 
That the effe&s of volcanos are more exten- 
five than philofophers, till of late, have been 
aware of, will, I am perfuaded, be readily ac¬ 
knowledged; and by the help of many obferva- 
tions lately made, we are enabled to account for 
various phenomena, which otherwife, mull have 
remained for ever unintelligible to the human 
fpecies. Of thefe, however, we (hall only take 
notice of thofe columnar pillars called Bafaltes, 
or Giant’s cauleways. If we carefully attend to 
all the phenomena, obfervable in thefe produc¬ 
tions of nature, we fliall find reafon to conclude, 
that they are nothing more than ciyftallizations 
of lava or matter, brought into a ftate of fufion 
by the heat of fubterraneous fires. 
If ever it could be faid, that nature feemed to 
imitate art, it is in the formation of the Giant’s 
caufeways in the north of Ireland, where every 
pillar appears to have been hewn by an artift, and 
placed fo clofe to each other, as fcarce to admit 
a pin betwixt them. Their general figures are 
pentagons, hexagons and heptagons. Pillars with 
more fides are to be met with ; their fides, how¬ 
ever, are by no means equal. Each pillar, accord¬ 
ing to its number of fides, muft be furrounded 
* Quere, what is the reafon why flint is generally found 
among chalk or calcareous earths ? 
