KiNAHAN.— The Possible Organic Origin of Quartz- Rock. 293 



respectively, very like those due to the upper edges of the layers 

 and to the spikes of the Algae in the silicious sinter of the 

 the Yellowstone. These can be seen in the specimens sent by 

 Weed, which have been presented, through Prof. O'Reilly, to 

 the Royal College of Science, Stephen's Green. 



In examining quartz- rocks it should be remembered that 

 in many places they have been considerably altered by 

 shearing, and consequently metamorphosis ; as is so con- 

 spicuous in the County Donegal. Here the older quartz- 

 rocks (Archaean) have been changed into a highly quartzose 

 gneiss ; while the newer ones, possibly Cambrian or 

 Ordovician (Caradoc), have been subjected to considerable up- 

 thrusting which has sheared the rock over each thrust plane, 

 into flags. In south-east Ireland, however, it is not so ; as 

 those associated with the Oldhamians in the Forth Mountain 

 and westward to Bannow, County Wexford, exhibit remark- 

 able markings on the surfaces of the different planes, also dis- 

 tinct changes of colour in the different shelves of rock ; which 

 changes of colour, in the modern sinter, are due to the growth 

 of plants in zones of different temperature. Worm-tubes have 

 not been recorded in any Irish rocks except those of the barony 

 of Kilmacrenan, County Donegal, near the Bloody Foreland, 

 and in the hills northward of Ramelton ; some of the beds in 

 the latter are sheared and the pipes now appear as elongated 

 compressed tubes. In the "Pipe quartzites " of Suther- 

 land, Scotland, there are remarkable assemblies of worm- 

 tubes ; hard to be accounted for, until Prof Weed's researches 

 have suggested their origin. They seem to have been extensive 

 colonies that flourished in large exposures due to hot springs, 

 similar to the silicious sinter plains of the Upper Geyser of the 

 Firehole River, but of larger dimensions, each worm segregat- 

 ing the silex and thereby forming a pipe. Various features in 

 different places in the different quartz-rock areas suggest 

 analogies with those of the modern rocks ; such as the Eagle's 

 Nest, Mulroy Waters, County Donegal, which, on view, has 

 a character similar to the sketch, fig. 53, in Weed's Bulletin. 

 Any microscopist who may take this subject in hand I will 

 aid, as far as possible, with information as to the best localities, 

 for research. 



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