Neighhourkood of the Gian.t*s Cauaeway, c^c. 37^ 



8dly. Our whynn dykes come in contact with a great 

 variety of diflerent substances, without producing such 

 efFect upon any one of them as might be expected froni 

 the contiguity of so glowing a mass ; hut however this 

 araument mav bear against the Folcunists, the Plntonists 

 will say it does not apply to them, for the chemical opera- 

 tions of nature are carried on in Dr. Hutton's subterranean 

 Jaboratorv very diflferentlv from what we see on the surface 

 of our globe : in the former Dr. Hutton says calcareous 

 strata are covsoUdaied by the operation of heat atid simple 

 fusion, and again, having proved that these strata had been 

 consolidated by simple fusion^ (page 253.) Dr. Hutton 

 however confesses it is not easy to comprehend this : "^and 

 to be convinced that this calcareous stone, which calcines 

 so easily in our fires, should have been brought into fusion 

 by subterraneous beat without sufTering calcination, "mus't 

 require a chain o( rcRsomng which every 07ie is not able 

 io comprelievd," (page 271.) 



But it is not necessary on this occasion to enter into the 

 mysteries of a laboratory, to which we have not access, nor 

 to calculate the force of Dr. Hutton's great agent com- 

 pression; for our observations on the contacts of the matter 

 of our whynn dykes with the substances they encounter, 

 being made on the surface of the earth, in the open air, 

 even admitting tho«e dykes to be formed as Dr. Hutton 

 supposes, his uncrupted lava is now become erupted, and 

 of course, to use his own words, *^ those substances which 

 palcine and vitrify in our fires, should suffer similar changes 

 when delivered from a compression which renders them 

 fixed." (Edinburgh Trans, page 280.) . 



I am aware I must fatigue your lordship by dwelling so 

 long upon the question of the igneou? origin of our whynn 

 dykes ; but as most modern writers and travellers call them 

 lava veivs, and ihe facts 1 have observed with much atten- 

 tion, induce me to combat so general and so popular an 

 -opinion, I hope you will excuse me for adding a fourth 

 ' argument, which I conceive to be conclusive. 



All substances, when ignited, are in a high state of di- 

 latation ; this is followed, when they cool, by a contraction, 

 7/77^ retraile, bv which they occupy le:?s space than they did 

 Kvhcn heated; of course, had our dykes been chasms filled 

 lip with glowing lava, when this material cooled and con- 

 tracted, it could no longer fill up these chasms as before, 

 but must crack and separate from their sides, Icavino- in- 

 tervals and disruptions^ byt nothing like this is observed, 



the 



