SCIENTIFIC NEWS. Sl?\ 



sand of which the outside of the tube consists. Both the 

 sand and the vitreous part of the tube scratch glass; and 

 on the latter, when viewed by a lens, there are seen small 

 air blebs, such as are common to imperfect vitrification. 

 Both are insoluble in sulphuric and nitric acids; infusible be- 

 fore the blowpipe without addition ; partially fusible on the 

 addition of boracic acid but; with soda a complete fusion 

 took place, and the residue was nearly soluble in water. 



A paper by Dr. Mac Culloch, M. G. S. on the vitrified Vitrrfed fom 

 fort of Dun Mac Sniochain, near Oban in Argyleshire, was kl Sc<wiaod " 

 read. In the discussion which some time ago took place re- 

 specting the vitrified forts of Scotland, the question on 

 which the two contending parties were most at issue was, 

 whether the vitrification was the effect of design or of acci- 

 dent. It occurred to Dr. M., that light might be thrown 

 on the subject by examining with mineralogical accuracy 

 the substances of which these structures were composed; 

 and noting the changes, which each had undergone, incon- 

 sequence of the fire; and also by observing whence the 

 stones had been derived, which were used in them. And 

 that the question of accident or design might be illustrated, 

 by examining iu the laboratory the degree of heat required 

 to produce the appearances in the stones, which actually 

 exist in these structures. 



The fort of Dun Mac Sniochain stands on a long narrow Fort of Dim 

 hill, which is nearly precipitous along three parts of its cir- M^c Siiioci^;« 

 cu inference; and at the other end it rises from the plain 

 with a very accessible acclivity. The walls, which are 

 nearly all at present buried under the soil, are about eight 

 or ten feet in thickness. They bear marks of vitrification 

 through their whole ^extent, but iu no case does it ap- 

 pear to have extended more than a foot or two upwards, and 

 the most perfect slags are found at the bottom of the foun- 

 dation. In the higher parts there are stones roasted by the 

 action of the heat, but unverified ; and at length the marks 

 of fire almost entirely disappear. The hill consists of al- 

 ternate beds of schistus and limestone, but the latter is the 

 predominant rock. It is perfectly insulated in a great al- 

 luvial plain. The mountains of Benediraloch, which bound 

 the plain to the west, consist of granite, gneis9, mica-slate, 



quart/ 



