On the Huttonian Theory of the Earth. 157 



not the flighteft indication of their origin ; whins, though they abound in Scotland, and 

 fome other countries, are, in comparifon of the former, but thinly fcattered over the fur- 

 face of the globe. Some refemblance betwixt them and lavas has been long noticed. I 

 fhall now briefly mention a few of the difcriminating chara£lers of the artificial and natu- 

 ral whins, which may in mod cafes prevent us from confounding them, or afcribing to 

 them a common origin. 



1. The natural whins, particularly Amygdaloides (vulgarly called Toadftones) frequently 

 contain calcareous fpar and zeolyte; now as the former contains fixed air, and the latter a 

 notable proportion of water, I hardly think Sir James, who profefles not to agree with 

 Dr. Hutton in all points, will allow thefe to have been vitrified or fufed. 



2. The natural whins, according to Dr. Kennedy's flatement, lofe 5 per cent, of water, 

 and other volatile matter, when heated to rednefs. It is not faid, whether the artificial 

 lofe any part of their weight by fuch treatment ; but it is plain they would not, fince even 

 the lavas of Catania and Piedmonte, though of ancient date,- loft none, as Dr. Kennedy 

 exprefsly notices, and has thus afforded an excellent criterion for diftinguifliing the long 

 contefted origination of thofe fubftances. 



3. As Sir James has negledted giving a compleat account of the external chara£l:ers of the 

 natural whins, which were the fubje£l of his experiments, as alfo of the regenerated, or 

 artificial whins derived from them ; and as I have not myfelf feen them, it is difficult for 

 me to compare thein with each other, and would, indeed, be impoflible, if fome account 

 of them had not been given by Mr. Piilet, in his valuable Journal Britannique^ copied into 

 the 5th Vol. of the new Rozier's Journal, p. 313. It is the refult of the examination 

 both of the natural and artificial whins by the Society of Natural Hiftory at Geneva. 



As to the grunftein, No. i. they remark, that it betrays not the leaft mark of an igneous 

 origin, but that the whins which Sir James produced from it, had every diftindlive cha- 

 ra£ler of a lava, and even of a porous lava. 



The Bafalt (or rather Trapp) on which the Caftle of Edinburgh ftands, is of a compa£l 

 ftrudure ; the artificial produced from it. Sir James tells us, fo greatly refembles it both 

 in colour and texture, that it would be difficult, or perhaps impoffible, to diftinguilh them, 

 but for a few minute air bubble!, diflinguifliable in the artificial. Neptunifts will, however, 

 confider this as a leading character of diftin£lion. The mineralogifts of Geneva add, that 

 the* colour of the artificial is deeper, and its hardnefs greater, than that of the natural. 

 If the fpecific gravity, and other chara61:ers of both were given, it is probable that other 

 differences might be perceived. It is only in thefe chara6ters that any difference can be 

 cxpeded, as the internal compofition muft be the fame in both. 



Of the remaining artificial whins I can give no account, their external charafters having 

 been omitted ; I cannot, however, pafs over the general inferences that Sir James deduces 

 from his experiments, namely, that " the arguments againft the fubterraneous fufion of 

 " whinftone, derived from its ftony character, feem now to be fully refuted," for not to 



repeat 



