372 ME. V. BALL ON THE PEOBA.BLE MODE OF TEAlfSPORT OF GRANITE 



The examination of these specimens has revealed the presence not 

 only of angular fragments of granite but also of schist, quartzite, and 

 vein-quartz, such as might have been derived from the metamor- 

 phosed Silurian rocks which rest on the granite near Dublin, and 

 are in one localitj^ exposed in a sea-cliff at the base of Ealliney hill. 

 As a rule, these fragments, though in some cases permeated with 

 calcareous matter, show little if any signs of decomposition ; the 

 surfaces of contact with the enveloping limestone are sharp and clean, 

 and the adhesion is ver}- firm. As will be observed, fragments of 

 fossils, especially of Encrinites, some being of very large size, occur 

 abundantly iu the limestone, together with the pieces of crystalline 

 rocks. 



Before proceeding to discuss what appears to have been the most 

 probable means of transport, I shall give a brief account of what has 

 been recorded by previous writers on the subject. 



Previous NotiGes. 



In the year 1851 *, the Rev. Professor Haughton published an 

 account of the occurrence of fragments of granite in the limestone 

 exposed in a quarry at Crumlin, near Dublin. They occurred, as 

 then observed, in one thin bed only, and were pretty uniformly 

 distributed. They varied from pieces about 8 inches in diameter, 

 down to the size of small grains of gravel; they were quite angular, 

 and showed no signs of having been rolled. The nearest granite, in 

 situ, is four miles off. 



Reference is made in this paper to another specimen from 

 Monkstown, co. Dublin, consisting of a rolled boulder of dolomitic 

 limestone, which contained fragments of slate as well as granite. 

 Dr. Haughton subsequently wrote : — " In 1851 I brought forward 

 at the Geological Society of Dublin a case of angular fragments of 

 granite, occurring in the Carboniferous Limestone of the Co. Dublin, 

 and explained the phenomenon by the supposition of the transporting 

 power of ice "' t. 



In 1864 ITr. Henry B. S. Montgomerj^ % described a quarrj' on the 

 banks of the Dodder, at Eathgar, near Dubliu, in which two strata 

 of limestone were met with, each containing imbedded masses of 

 granite clustered together; these two strata were parted by two 

 others, in which no granite was found. It is stated in this paper, 

 that a second bed had been met at the Crumlin locality, separated 

 from the one mentioned above by twenty separate beds. It was 

 remarked by llr. Montgomery that the fragments always had the 

 heavier ends downwards, as though they had fallen through water 

 and subsided in mud. 



In 1862 Prof. Jukes § refers to the subject thus : *' The probable 



* Journ. Geol Soc. of Dublin, vol. v. p. 113. 



t Appendix to the Voyage of the 'Fox' in the Arctic Seas, By Oapt. 

 M'Chntock, ^.'N., LL.D., p. 395. 



X Journ. Eoy. Geol. Soc. Ireland, vol. xi. (N. S. vol. i.) p. 15. 

 § Manual of Geology, new edition, 1886, p. 298. 



