610 KEPORT 1881. 



years ago, was suggested by Jukes, while now it is positively asserted, but solely 

 on lithological characters. The author pointed out that, although these rocks 

 lithnlogically were very like Laurentians, they were more like Huronians, Logan's 

 description of the latter being very suitable for those of Donegal. He also 

 pointed out that it was unnecessary to make vague assertions, as the stratigraphical 

 position of the rocks ought to be easily worked out, either by starting from the 

 Pomeroy fossiliferous rocks, or from the fossiliferoua rocks found in Donegal by 

 Dr. King ; but that, at the same time, the work must be much bettpr and more 

 correctly done than that in the neighbourhood of Pomeroy, where the unaltered 

 fossiliferous beds are classed with those they lie on, although the latter were 

 extensively metamorphosed, contorted, upturned, and denuded, prior to the fos- 

 siliferous rocks being deposited on them. N.E. Antrim — rocks supposed to be of 

 the same age as the older rocks near Pomeroy {Upper Cambrians). 



3. Jb'fe in Irish and other Laurentian Bocks. Bij C. MooRE, F.G.S. 



The author drew attention to certain forms found by a microscopic examination' 

 of specimens of certain Laurentian and other Palfeozoic limestone prepared by tri- 

 turation, solution in acid, and washing. These forms were clearly those of organic 

 structures, some apparently hairs and others feather-barbs. The author considered 

 that he had taken precautions to eliminate sources of error, through admixture 

 of foreign materials ; and he was led to think that the organisms belonged to the- 

 rocks. 



4. On the occurrence of Granite in sitii, about 20 miles 8.W. of the Eddy- 

 stone.^ Bij a. R. Hunt, M.A., F.G.S. 



The author stated that during the past year he had received four specimens of 

 rocks from the English Channel, trawled by Mr. W. M. Bayne's fishing vessel, the 

 Pelican. Of these, three were trawled as detached blocks, and were respec- 

 tively a gabbro, an actinolite rock, and a diabase : the fourth was a fragment of 

 granite brought up in October 1880, about 20 miles S.W. of the Eddystone, after the 

 vessel had been about three hours fast in what the crew iirst supposed to be 

 a wreck. This fragment, which is about two inches in thickness, shows a clean 

 fracture, has marine organisms on both sides, and has undoubtedly been detnched 

 from a submarine rock. There is no absolute proof forthcoming that this rock is 

 in sitii, but from the fact that the fishermen knew of no rocks in the neighbour- 

 hood, it can scarcely be a large erratic Ij'ing uncovered at the bottom of the 

 English Channel, as such an obstruction would soon be found out and avoided.. 

 If an erratic, and too large to be moved by the hauling gear of a 60-ton vessel, it 

 must be buried in the sand, and in this respect ditfer from the detached blocks 

 described last year, which lie strewn on the surface of the Channel bed to the 

 southward of the Bolt and Start. In mineral composition this granite agrees with 

 the gneiss of the Eddystone and the gneiss of the Shovel Ileef in Plymouth Sound,, 

 all these rocks being couiposed of orthoclase and plagioclase, the two micas and 

 quartz, without either hornblende or schorl. The fact that the Shovel gneiss does 

 not alter the Devonian rocks of Plymouth, the author considered an indication that 

 these typical Channel gneisses are of pre-Devonian age. 



5. Some Observations on the Causes of Volcanic Action. By J. Prestwich, 

 M.A., F.R.S., Professor of Geology in the University of Oxford. 



Considerable difference of opinion still exists as to the cause of volcanic action. 

 The hypothesis, liowever, generally accepted in this country is that of the late 



' See ' Notes on the Submarine Geology of the English Channel,' Trans. DeiK 

 Assoc. 1881. 



