Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/283

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Dr. Mac Culloch on the Vitrified Forts of Scotland.

This variety is fusible, and from this unquestionably the vitrified portions had originated. It is here that a part of the rock has been cut down, very certainly by sharp tools, for the purpose of scarping one side of the fort. There is no bed of foreign fragments on the top of the grauwacke, and no covering but the common soil. I know not what conjectures we can form about this fort, except that the same attempt has been made, but has failed from the deficiency of proper materials. I confess that the consideration of the requisite heat inclines me as much in this case as in the former to the original supposition, and confirms in my mind the notion that the vitrified forts of Scotland are the effects of design.

Since the above account was written, two circumstances have occurred to me which seem to afford additional evidence of the truth of the opinions I have held respecting the vitrification of these buildings.

The first is an article in the 12th vol. of Nicholson's Journal, p. 313, quoted from the report of a French engineer (M. Legoux de Flaix), describing a method of building practised in Hindustan. In this process a wall of brick earth is erected, which is then surrounded by a coffer filled with combustibles. As the combustion proceeds fresh fuel is added, until the whole wall is baked into one solid brick. The coincidence of the effects of this actually existing process with those of one long since forgotten, seems to prove almost to demonstration, that similar means have been practised in the ancient military works of Scotland to produce structures so analogous to those now commonly used in India, and that the “baking” of buildings in this country must be considered in the light of a lost art.

The other is to be found in the history of Gatacre-house in Shropshire, (now unfortunately pulled down) of which a slight and

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