178 Scientific Proceedings, Royal Dublin Society. 



Paper on Marbles (vol. v., p. 405). Some of the steatytes and 

 camstones have been locally used for lining furnaces and the 

 like ; but as yet there has not been any regular trade in them> 

 although they seem capable of being cheaply wrought into fine 

 bricks. 



Typical quartz- rock (Greisen, Cotta) is sometimes apparently 

 an intruded rock. On account of its usual splintery, rubbly 

 nature, it is not generally fit for building purposes, except for the 

 rudest walls. 



Gneiss is generally a hard, durable stone ; and some, if regu- 

 larly jointed, can be raised in naturally square blocks of both 

 large and small scantling, suitable both for heavy and for light 

 work. It is capable of long and heavy bearings. This rock is 

 usually difficult and expensive to dress, quickly wearing out the 

 tools. All samples will dress on the foliation surfaces ; but many 

 will not dress, though some may be sawn, across these. 



Grood schist, like slate, is durable, and if naturally jointed 

 makes good building-stones, as it rises in more or less flat-bedded 

 blocks. In some places the mica schists are ferruginous {.ferri- 

 ferous micalyte) and rapidly assume the appearance of having been 

 burnt. 



Many of the fine-grained, or the close granites, are eminently 

 suitable for paving-setts, on account of their hardness and the 

 readiness with which they split, as also some of the elvans and 

 whinstones ; but in order to be useful in this way, the stone 

 must not only split easily into the required sizes, but it must not 

 be liable to become slippery when worn by traffic. Many stones, 

 eminently suitable for paving in all other respects, become dan- 

 gerously slippery, even after a little wear. 



A practice has been lately introduced of breaking up the waste 

 of granite quarries into gravel and sand for walks, or for the manu- 

 facture of granite concrete blocks for streets, drives, and walks. 

 This granitic concrete is much superior, in every way, to asphalt ' f 

 but it has not come into general use, being much more difficult to 

 repair when a pathway is cut across to lay down water, gas, or 

 other pipes. This, however, might be remedied if the concrete 

 were manufactured in narrow blocks, say eighteen inches wide, 

 one course of which might be raised without interfering with the 

 rest. 



