268 Proceedings of the Royal Physical Society. 



by placing vegetable matter in moist clay, and exposing to 

 heat. DaubreVs observations made at the thermal springs 

 of Plombieres were next mentioned. These issue, with a 

 temperature of about 172° Fahr., from a porphyritic granite 

 in the mountains of the Voges. To convey the water of 

 the springs to the baths, which the Bomans had built there, 

 a structure of brick and sand had been erected. Through 

 this the water had trickled. On breaking into the mass 

 numerous minerals of the zoolite family were found, but 

 chiefly Apophyllite and Chabasite. Mr Livingston then 

 mentioned the extensive changes effected by the juxtaposi- 

 tion of certain rocks, and especially the phenomenon termed 

 Endomorphism by Fournet. He then discussed the bearing 

 of these and other facts, and showed that, though the hypo- 

 thesis of a central fire would undoubtedly explain much, 

 yet that it would not all. If heat were the Only agent in 

 these changes, he asked why did they not take place accord- 

 ing to the known laws of the propagation of heat and the 

 conductibility of rocks ? That water had to do in effecting 

 these changes was evident from the occurrence of chiasto- 

 lite, augite, garnet, and felspar in sedimentary rocks. The 

 presence of water chemically combined in the masses ejected 

 by volcanoes was a proof that it played an important part 

 in the phenomena that take place at great depths. He then 

 referred to the facility with which minerals, and especially 

 the silicates, can be formed when water is present, to Dau- 

 breVs production ofWollastonite,to his process of forming the 

 anhydrous silicates in the moist way, and his production of 

 a substance like mica and chlorite. Mr Livingston believed 

 that these researches invite us to hesitate before we commit 

 ourselves to the views of the igneous rocks at present in 

 vogue, and expressed his conviction that the faith of geolo- 

 gists, after much weary tossing between fire and water, would 

 finally settle down somewhere between these two extremes. 



A conversation followed on the plutonic and aqueous 

 agencies in the formation of rocks, and on the probable 

 aqueous origin of granite, in which Professor M'Donald, Mr 

 Alex. Bryson, and others, took part. 



