118 G. H. Kinahan — On Faults in Strata. 



jboundary were straigM, T stould conclude tbat tlie discovery of sucli 

 a natural junction as that described by Mr. Medlicott proved, not the 

 absence of a fault, but simply that in that spot the newer rocks had 

 been denuded away from the neighbourhood of the fault, and the 

 natural boundary exposed, I do not mean for an instant to assert 

 that this is the case at the foot of the Garo hills ; all I contend is, 

 that the evidence offered does not, to my mind, disprove the existence 

 of a fault. 

 Chanda, Central Provinces of India, Jan. 3rd, 1870. 



VI. — On Faults in Stbata. 

 By G. H. Kinahan, M.E.I.A., F.E.G.S.I., &c. 



THE acute observation of the late Professor J. Beete Jukes, combined 

 with his power of reasoning from Nature, and by Nature's laws, 

 enabled him at once to be capable of explaining the relations of 

 complicated strata, over which others might puzzle for months : 

 neither was he unwilling to impart his knowledge to others, for 

 nothing seemed to give him greater pleasure than teaching and 

 explaining away difficulties, by pointing out the similarity between 

 the former and present agents at work fashioning the surface of our 

 earth. 



In Mr. Medlicott's paper " On Faults in Strata," ^ similar arguments 

 to many of those of this eminent geologist, against the indiscriminate 

 use of faults, are given. Moreover, Mr. Jukes often impressed on 

 his assistants that which is here so well put forward by Mr. Medlicott 

 — '" The result may look very well, but it will leave us no wiser as 

 to the natural history of the rocks." 



At the present day, the marginal rocks of groups, now in the 

 course of formation, are as often being deposited at the base of, or 

 against, a cliff as elsewhere ; and if now, why in the ages long past 

 should not similarly placed rock have been formed? That they 

 should exist seems probable, and the following instances in Ireland, 

 worked out under the superintendence and with the able assistance 

 of Mr. Jukes, may be mentioned. In the county of Limerick, lime- 

 stone and other rocks of the Carboniferous age are deposited against 

 masses of contemporaneous Igneous rocks.^ In Slieve Bloom, the 

 mountains at the border of the Kings Co., in the hills southward of 

 Nenagh, Co. Tipperary, in Slieve Aughta, the mountains at the junction 

 of Clare and Gal way., &c, &c., the ba«al sandstones and conglomerates 

 of the Carboniferous period [or the Old Eed Sandstone] were depo- 

 sited against cliffs of Lower Silurian rock ^ ; while in the promontory 

 of Dingle, Co. Kerry, the basal bed ["the Inch conglomerate"] of 

 " the Dingle beds" is deposited against and at the base of ancient 

 cliffs of Silurian rocks* ; and in the country adjoining the north part 



I Geol. Mag., Vol. VI., p. 341, August, 1869. 



'^ Memoirs of the Geological Survey, Maps and Explanations of Sheets 143, 144, 

 153, and 154. 



» Ibid, Maps and Explanations of Sheets 118, 124, 125, 126, 127, 134, 135. 

 * Ibid, Maps and Explanations of Sheets 160, 161, 171, 172. 



