420 PROCEEDINGS OP THE GEOLOGICAL SOCIETY, [April 26, 



water to flow over its surface to the ends of the branches of the ar- 

 borescent kind pointing from the sides in all directions. In many 

 instances the branches were bent ; and in the one which is drawn 

 full size in fig. 3 it had grown into the form of a ring — undoubtedly 

 the result of the stem which had first shot from the side horizontally 

 being unable to sustain its own weight. It is impossible for water 

 to flow over the surface of such a figure to the point or end of the 

 stem. Besides, had the water flowed over the surface hke ordinary 

 stalactites, the stems would have been thickest at the base. Nor is 

 it possible that any of the long stems could have been knobbed. Again, 

 in the branched varieties which hung from the roofs of the cavern 

 there were no phenomena to warrant the conclusion that those pure 

 white and elegant forms could result from water streaming very 

 slowly over the surface. 



We are therefore compelled to adopt the theory of a circulation, 

 through the pores of the spar, of fluids holding its component parts 

 in solution, as the only one which wiU harmonize with the varied 

 phenomena found connected with the two caverns in which this 

 mineral was formed in the Dufton Fell and SUver Band Mines. 



In connexion with this theory there is one fact too remarkable to 

 be passed over, which occurred in both caverns, namely, that after an 

 isolated piece of arragonite was broken oif the hard rock, a thinly 

 spread gush of water flowed over the fractured part for a few minutes, 

 gradually blended with the moisture on the damp sides of the cavern, 

 and then totally disappeared. It would appear that some force 

 attracted the water to the root or base of the arragonite ; and when 

 the connexion between the arragonite and the rock was broken the 

 water flowed from the fracture like sap from a wounded tree. 



Prom an examination of a great number of cases of arragonite in 

 an inceptive state, it appeared that carbonic acid had been evaporated 

 from the sides of the cavern, leaving a very thin deposit of lime ; and 

 that to this thin deposit the moisture is drawn or attracted to circu- 

 late through its pores, effecting the development of either the curi- 

 ously rounded masses or stems. It may be asked. Why is not this 

 mineral always found growing on the damp sides of limestone-caverns 

 or joints ? Perhaps this question cannot be satisfactorily answered 

 at present. I have already observed that all the places where I have 

 found arragonite were in or near veins in which the minerals de- 

 posited at a former period were undergoing decomposition. And if 

 it be still further questioned why arragonite is not formed wherever 

 decomposition of vein-minerals is being effected, I can only reply, 

 that its growth may be promoted by a number of causes very deli- 

 cately balanced ; and I am incHned to suppose that common air 

 and carbonic-acid gas, combined in proportions which rarely continue 

 in nature through long periods of time, constitute an atmosphere 

 essential. It is difficult or impossible to ascertain the exact consti- 

 tuent parts of this atmosphere ; for the openings made by mining 

 operations admit a purer air, or one containing a less quantity of 

 carbonic acid. A large quantity of this gas was evidently present 

 in the Dufton Pell cavern, for when it was first opened into the 

 candles were with difficulty kept lighted. 



