260 Proceedings of the Royal Physical Society. 



reduced to in the infancy of tlie arts. This discovery of yours 

 will serve to detect an error that several ingenious naturalists 

 have fallen into, of burning mountains found in Scotland, 

 verified, they say, by the burnt remains still to be traced. I 

 suspect that these remains are no other than the debris of the 

 vitrified forts you mention." 



The only remark called for here concerns the opinion that 

 the forts must have been erected before mortar was known. 

 Most writers who have referred to these forts, in the course of 

 the last hundred years, have repeated this opinion of Lord 

 Karnes; but the inference is not warranted. All that the 

 employment of vitrifaction entitles us to say is, that it was 

 found most suitable for the locality where the fort was erected. 

 Mortar may or may not have been used contemporaneously 

 with this process. The value of Williams's pamphlet is 

 enhanced by the publication in the appendix of a description 

 of " Craig Patrick," by James Watt, and a letter to Williams 

 from Black the chemist. Watt says of the materials, that 

 they '' greatly resemble the cinders or clinkers produced in a 

 lime-kiln, being in some parts a vitrified, spongy mass, with a 

 glossy surface ; and, in other places, when it has been broke 

 into for a small depth, you may see calcined, though unvitri- 

 fied, matters mixed in large pieces among the spongy slag. It 

 is evidently the native rock vitrified ; and the granite parts 

 seem to be the only ones which have come into fusion, and 

 have formed the slag." Black points out the fusible quality 

 of whinstone and granite, of coarse limestone, of " pudden 

 stone " and sandstone, when they contain certain proportions 

 of iron. He adds, "As the whole country was anciently a 

 forest, and the greater part of it overgrown with wood, it is 

 easy to understand how those who erected these works got 

 the materials necessary for their purpose." Macculloch, in 

 his " Western Isles," describes the vitrified forts. Dun MacSnio- 

 chain and Dunadeer, as consisting of easily fusible rocks, 

 the former being built chiefly of conglomerate, the latter 

 of stones gathered from the plain containing hornblende in a 

 black variety of granite. Later we are indebted to Dr J. 

 Jamieson for a paper on the vitrified fort of Finhaven, and to 

 the late Dr John Stuart for a summary of opinions concerning 



