375 Account of the IFhynn Dykes in the 



Dr. Hamilton on behalf of the /-'o/raw/VA?, andDr.Hiittoii 

 the great advocate for the FliUomc system, arc more ready 

 at their expcdicnrs ; the first of these forms our whxnii 

 dykes bv pouring in erupted lava at the upper aperture of 

 mightv chasms ; while Dr. Mutton conceives these chasms 

 were fiTled up by his own unerupted lava, forced up at the 

 lower. 



In discussing the opinions of these gentlemen, I will 

 make them the most liberal concessions; for instance, I 

 will concede to both, that they have discovered the process 

 by which nature has formed chasms of immeasurable 

 length, innneasurable depth, and of inconsiderable, tliough 

 uniform, breadth. 



i will concede to Dr. Harhilton that he has brought to 

 the edge of the chasms his lava, *' th's foreign substance, 

 which issuing from the vast mass of basahes that forms 

 the northern extremity of Fairhead, has descended over the 

 adjoining strata,'' and that he has it ready *' to Jill up each 

 deft and vacuify." (Ham. Antrim, let. 5, part I .) 



I will also admit in favour of Dr. Hutton, that he has 

 his unerupted lava ready at the bottom of these chasms, 

 that he has his machinerv prepared for forcing it up, and ^ 

 that he has surmounted his great difficulty, and discovered 

 a mode of supporting such a mass when raised ; a point 

 upon which, having failed himself, he would discourage 

 others from forming conjectures. (Edinburgh Trans, vol. i. 

 page 285.) 



Notwithstanding these concession?, it will not be difficult 

 to show that these gentlemen have not discovered the secret 

 of nature in the construction of these singular walls, and 

 that they were not formed by liquid lava filling up mighty 

 chasms. 



1st. Many of our contiguous dykes differ materially from 

 each other, yet iheir proximity is such, that, according to 

 the theory of either Dr. Hamilion or Dr. Hutton, they 

 must have been filled up from the same source, and with 

 the snme material. 



2dlv. Many of these dykes, both in Ireland and Scot- 

 land, show a material difference between their middle parts 

 and their sides, both in grain and ii^ternal principle of 

 construction ; the chaiige too is not gradual, but per 

 sai'.um, as if the dissirrnlar parts were separated from each 

 other by planes parallel to their sides: all this is perfectly 

 incompatible with the high state of fluidity in which rhe 

 lava must have been, to enable it to fill up vast chasms of 

 such diminutive breadth. 



3dly. 



