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(9) By Lieut. H. L. NORTON-SMITH, F.S.A. Scot., the Author. Armorials of the County of Orkney. Illustrated by A. M. Traill. 8vo. 1902.
(10) By JAMES MACKENZIE, F.S.A. Scot., the Author. Life of Michael Bruce, Poet of Lochleven. 8vo. 1905.
(11) By the TRUSTEES OF THE HUNTERIAN Coin CATALOGUE FUND. Catalogue of Greek Coins in the Hunterian Collection, University of Glasgow. By George Macdonald, M.A., LL.D. Vol. iii. 4to. 1905.
(12) By GEORGE MACDONALD, M.A., LL.D., the Author. Coin Types: their Origin and Development. Being the Rhind Lectures for 1904. 8vo, 1905.
(13) By the KEEPER OF THE RECORDS OF SCOTLAND. Register of the Privy Council of Scotland. Edited by Professor P. Hume Brown, LL.D. Vol. vi. New Series. 1635–37.
Accounts of the Lord High Treasurer of Scotland. Edited by Sir James Balfour Paul, Lord Lyon King of Arms. Vol. vi. 1531-38.
There were exhibited :
By W. J. GRANT, Esq., of Beldorny Castle. A Collection of Thirty Arrow-heads of Flint, found in various parts of Aberdeenshire.
The following Communications were read :
ON VITRIFIED FORTS, WITH RESULTS OF EXPERIMENTS AS TO THE
PROBABLE MANNER IN WHICH THEIR VITRIFICATION MAY HAVE BEEN PRODUCED. By Lieut.-Col. A. B. M'HARDY, C.B., Vice-President.
In asking the attention of the Society to some observations on the subject of vitrified forts, it is not necessary for me to rehearse what has already been written about them. The mystery of their origin has never been cleared up in a satisfactory manner, although they have attracted the attention of many antiquaries.
The first printed notice of vitrified forts seems to be that found in Pennant's Tour in Scotland, published in 1774, where he says he saw on the top of a hill near Fort Augustus, in a small oval area, a quantity of stones cemented with almost vitrified material, and he could not make out if they came from a volcano or a forge.
Shortly after this we have Williams' letters, in which he described the forts of Knock Farrell, Craig Phadric, and others; his theory being that a fire had been made along each side of the wall, and the stones thereby vitrified ; but he puts the suggestion forward with hesitation.
At that time it was believed that vitrified forts were to be found only within a very small area in Scotland, but since then (1777) vitrification has been observed in the remains of old fortifications in many different parts of Scotland, in Ireland, Germany, Austria, and several regions of France. Indeed, it is probable that this list of the distribution of socalled vitrified forts is still far from being complete.
It is therefore clear that vitrification was well known among various races, of whom it may be said, without defining in any way the exact epoch when the work was done, that they must have been in a primitive state of civilisation.
The scheme on which the forts in Scotland have been disposed has led me to consider the time of the Vikings a probable date for some of them.
What is termed a vitrified fort of a normal character may be described as a mound or parapet, roughly circular in plan, or traced as an irregular polygon following more or less closely the edge of the flat top of a hill or ridge.
If we examine the section of the parapet, we find on the soil a mound of loose stones, varying in size, say 2 feet deep; and overlying the loose stones, a layer, say 2 to 3 feet thick, of similar stone held together by a lava-like substance obtained by the complete or partial fusion of some of the stones in the heap.
This may suffice for giving a general idea of the section of the parapet, but more investigation is necessary, by careful excavation on the ground, before the exact section of the parapet of a vitrified fort is known, and probably considerable variety will be found.
The vitrified material is in most cases now found covered on the top with a little soil and vegetation. The vitrified layer is not found, I believe, perfectly continuous in every part of the parapet, and often appears only at certain points, notably at Tap o' Noth.
The size of the forts varies greatly, from the large fort just mentioned to a heap of stone with no indication of an enclosure which could be called a fort.
In position, the vitrified forts I have seen (seventeen) in Scotland are situated either near the coast where it is deeply indented by the sea, or at inland points which open up a large valley, or a group of valleys radiating from a common centre.
The rocks which seem to melt to form the slag are chiefly micaschists, felspathic rock, diorite, and moine schist, while the granite has not been affected in the same way by the process. Through the kindness of the late Mr Ivison Macadam, I am able to give a chemical analysis of the slag from the following places :
We now pass on to consider how it is that the vitrification of these forts has come about. Various opinions have been expressed : (a) Some that it was done incidentally as the result of beacon.fires,
or great fires for religious or other purposes. (6) Other authorities see in these forts the intended result of structural
operations, believing that the intention was to strengthen the parapet by fusing together the small stones of which it was
composed. The interdependence which can be observed in some of the groups of vitrified forts lends support to the view that they were used for signalling purposes, and I think that that may be assumed as certain, although there seems reason to suppose that they only were used for that purpose any more than other forts in similar situations, which, being composed of different and more refractory materials, have not left the result of the fires so distinctly marked by the slag.
(a) I shall refer to the possibility of producing vitrification by beaconfires later on.
(6) Turning at present to the view that the vitrification was inten