of the Vicinity of Dublin. ' 309 



The flat calcareous country of the tieighbourhood of 

 DubHn is very widelv extended in vavioLn directions : it 

 passes round ihe mountainous tract above mentioned at its 

 nonh-uestcrn angle, and reaches with liule interruption, 

 in a southern direction, through the counties ot Kildare and 

 Carlow, to the Foot of the hills of the Kilkennv-coal -district; 

 and to the south-west, through the Kin.g's and Queen's 

 counties, to the foot of the Shebh-blooni mountains. It 

 has also considerable extent ti^wards the north and west. 



In the parts of this plain more immediatelv in the neigh- 

 bourhood of the city, the prevaihng rock is that variety of 

 lime.Uone to which Mr. Kirwan has given the name of 

 Ca/p, of which an excellent description and analysis have 

 been published l)y tlie Hon. Mr. Knox*: Bui in several 

 parts of the flat country, limestone of the ordinary kind 

 abounding in petri tactions is also to be iTiet with. 



In the course of the river Dodder, between the village of 

 Milltown and Cla^ison's Bridge, the calp appears to alter- 

 nate with beds of granular 77iagnesian- limestone in its cha- 

 racters perfectly resembling some of the substances that oc- 

 cur in various parts of England, which are described as 

 affording a lime injurious to vegetation, in Mr. Tennant's 

 very important paper "on different sorts of lime used in 

 agriculture f." The magnesian stone at Milltown agrees 

 with the calp and ordinary limesione of the adjoimng 

 country in containing petrifactions, although less com- 

 monly ; and like them also it has frequently imbedded in it 

 masses of siliceous matter, (the "Lydian stone," or a va- 

 riety of horn'^tone of Werner.) 



The beds of calp and limestone near Dublin, are in ge- 

 ..neral but liitle inclined to the horizon ; but they often ex- 

 K"ibi( maj-ks of dis!oea(ir)n •, and in some places are singu- 

 larly inflected, as is remarkably the case with those observ- 

 able in the bank of the river Liffey, near the bridge at 

 Luca7i. 



The petrifactions which abound in several parts of this 

 calcareous cf)untrv t ; the beds of calp, and of magnesian 

 limestone, and the siliceous masses above mentioned, af- 

 ford some of the features that mav assist in deciding to 

 which of the " formations" of Werner it'is to be referred, 

 or whether it properly belong to any of them : a point of 



• Trans, of Royal Irisli Academy, vol. viii. p. 207. 



f Pliilosiipliical Transact ions 1799, or Philusophical Magazine, vol. v. 

 pa^e '.'09. 



JThe qunrries at St. Dnolai^li's, and in the neighbourhood of FelHnt, 

 afl'urd very pcrlect ipecimeuti of petrifaciious, and in great variety. 



some 



