83 



6tre comptes, on peut a present concevoir 1'esperance de voir chacun 

 des dykes de cette tie individuellement e"tudie", numerote, decrit et 

 enregistre" dans un catalogue descriptif et raisonne, analogue a celui 

 que j'ai aujourd' hui 1'honneur de mettre sous les yeux de la Societe" 

 Koyale."* 



We are not able to state how far this estimate may be correct. No 

 one has followed out the suggestion made in the last sentence ; the 

 labour implied in the inquiry would scarcely be rewarded by the 

 scientific value of such a catalogue. 



Mr. James Napier, of Glasgow, has published a short paper on the 

 dikes between the bays of Brodick and Lamlash in the Edinburgh New 

 Philosophical Journal, New Series, vol. ii., No. 1, July, 1855, accom- 

 panied by a map, on which the dikes are laid down. He reckons 

 altogether fifty-four dikes as visible along the shore, but considers 

 that not a few may have escaped his notice. " Struck," says Mr. 

 Napier, " by the large number of trap dikes cutting through the 

 sandstone, in a direction at right angles to the sea line, it occurred to 

 me that if such dikes continued round the coast to Lamlash, and still 

 at right angles to the sea line, they must in all probability have pro- 

 ceeded from a common centre, lying somewhere between the two 

 bays." To test this idea by observation, he measured and marked 

 clown the position of every dike, and the result confirmed his " antici- 

 pation, that they proceeded from one, or possibly from two centres." 

 A similar idea would be very likely to occur on examination of M. 

 Necker's map, which certainly Mr. Napier had not seen, else he 

 would have mentioned it. The notion of radiation from a common 

 centre we do not, however, find alluded to in M. Necker's paper. 

 Mr. Napier seems disposed to assign two centres one for the fels- 

 pathic dikes, and another for the hornblendic both lying inland 

 towards the Lamlash road. Prolonging the directions of the two 

 principal felspathic dikes on the shore, he finds that they would meet 

 near the claystone quarry on the Lamlash road, about a mile from 

 Springbank ; and here he would place the felspathic centre ; the 

 hornblendic he does not so definitely fix. 



Now, analogies in support of this view can certainly be drawn 

 from districts of recent volcanic action, where fissures radiating from 

 a vent, or focus of disturbance, are seen to be filled with basaltic lava 

 and other igneous matters ; and the same may doubtless have occurred 



* Documents sur les Dykes de Trap d'une Partie de 1'ile d'Arran. Transactions of 

 the Royal Society, Edinburgh, vol. xiv., Part 2, 1840, p. 684. Extra copies of this paper 

 and accompanying map were thrown off, and are still to be had. It is a model of patient 

 and generally accurate research. 



