3(U Scientific Intelligence — Geology. 



stance is probably produced as the casting or impress of included 

 vapour or gas. Sometimes the flaws in coarse materials, such as 

 porphyry, have a specular aspect, owing to a film of anhydrous 

 peroxide of iron. Illustrative examples were exhibited, and refer- 

 ences made to various localities around Edinburgh, where the 

 whole phenomena offlaiued structure were well displayed. 



In proceeding to consider still farther the physiology of rocks, 

 Dr Fleming proposed in the second part of his communication to 

 confine himself to the illustration of — 



1st, The Columnar Structure. — After enumerating examples of 

 this structure, as occurring in the neighbourhood of Edinburgh, 

 in candle coal, sandstone, clay, ironstone, clinkstone, claystone, 

 greenstone, and basalt, he exhibited examples of similar appear- 

 ances in oven soles and fragments of the walls of vitrified forts. 

 The ordinary explanation of this structure as the result of cooling 

 from a state of fusion he pointed out as unsatisfactory, even in 

 the case of basaltic pillars, and inapplicable to similar appear- 

 ances as occurring in sedimentary rocks. He considered the 

 whole phenomena explicable as connected with one cause, viz., 

 shrinkage, arising from the escape of aqueous or volatile mat- 

 ter. 



2d, The Cone in Cone Structure. — Examples of this structure 

 occur in impure ferruginous limestone at Joppa, the Water of 

 Leith, and other places, in connection with the coal measures. 

 Dr Fleming referred the origin of this structure to shrinkage, con- 

 joined with a certain amount of molecular aggregation or crystal- 

 lizing influence. — (Proceedings of the Royal Society, Edinburgh.} 



9. Almaden Mine, California. — The process of extracting the 

 metal from the ore is very simple. The ore is placed in the fur- 

 naces, where a gentle and regular heat is applied. As it diffuses 

 itself through the ore, the quicksilver contained in it sublimes, and 

 is afterwards condensed, and falls by its own weight, trickles down 

 and out at little pipes leading from the bottom of the cham- 

 bers of the furnace, and empties into vessels so situated as to re- 

 ceive it. From these pipes we saw the quicksilver falling more or 

 less rapidly in large drops. In one vessel there must have been 

 from 15 to 20 gallons of quicksilver. About 1000 flasks per 

 month are manufactured, each flask containing 75 pounds, making 

 75,000 pounds per month. The flasks are all of wrought iron. 

 The time occupied in filling the furnace, and extracting all the 

 metal from a furnace full of ore, is about one week. When this 

 is accomplished, the furnace is opened that the mass of rock may 

 be removed to make way for another batch of ore. — (American 

 Journal of Science and Arts, vol. xvi., No. 46, 2d Series, p. 137.) 



