Fig. 43.—Portions of Iron Saw (1⁄4).
About 25 yards south of the crannog I observed a row of stakes in an open drain running towards the nearest land, and the tops of others in the grass, which from their arrangement suggested the idea that they were part of a gangway which formerly extended between it and the shore. This is one of those points not examined when our operations were interrupted by the severity of the weather.
The principal relics found beyond the inner circle row of piles consist of portions of a metal saw (Fig. 43), three flint implements (Figs. 63, 64, and 65), and two bundles of the fringe-like apparatus made of moss, besides those found in the refuse-bed.
2. Refuse-Bed.—The refuse-bed lay at the south-east side of the crannog (see Plan), just at the corner of the central log pavement, and consisted chiefly of gritty ash, decayed bones, and vegetable matters. It extended from the inner circle of stockades to within a few feet of the outer trench. Its breadth would be about 10 or 12 feet, and its length from east to west nearly double that. Its surface was from 3 to 4 feet below that of the field, so that its average depth would not be much short of 3 feet. Some important relics were found here, such as metal instruments and daggers, two fibulæ, several wooden vessels, and a few bone implements. It is noteworthy that the metal objects were all comparatively near the surface of the midden, and also that no boars' tusks or teeth were found in it except at its very lowest stratum.
It was ascertained, through the careful inspection of the Rev. Mr. Landsborough, that some of the large bones, especially leg-bones, contained in their cavities and interstices beautiful green crystals, of which I have collected some fine specimens. According to the analysis of Mr. John Borland, F.C.S., F.R.M.S., they are Vivianite, regarding which he writes as follows:—
"Vivianite.—A phosphate of iron, of somewhat definite composition, arising from the varying degree of oxidation of its base and state of hydration.
"It is found in two conditions—Amorphous and Crystalline—the former not uncommon, the latter rare. The amorphous has been frequently described under the name of blue iron earth; the crystalline was first named, and its relationship to the amorphous pointed out, by Weiner in Hoffmann's Mineralogie, about the year 1818 or 1820; the name being given in compliment to a Mr. Vivian of Cornwall, whose attention was first directed to the mineral.
"It has also been found at Bodenmais in Berne, and in several localities in America.
"Bischoff, in his Elements of Chemical and Physical Geology, as translated for the Cavendish Society, vol. ii. page 35, refers to a paper communicated by Von Carnall to a meeting of the Niederrheinischen Gesellschaft at Bonn, on the 3d December 1846, wherein mention is made of a remarkable instance of the occurrence of this mineral in the Scharley calamine mine, Silesia, which it was presumed was originally worked for lead.
"At a depth of 8 or 9 fathoms the skeleton of a man was found, and on breaking one of the bones crystals of vivianite became visible in the interior. A thigh-bone, when sawn through, showed crystals projecting from the inner surface, and others which were loose. The length of time the bones had lain there was unknown. The working of the Scharley mine began in the thirteenth century, and at the date of the communication had been discontinued for nearly three hundred years.
"Bischoff, however, advances the suggestion that, as the shaft may have been sunk in search of calamine, and not for the working of the lead, the age of the bones would not be so great as might at first be assumed. An analysis of the few crystals placed at my disposal leads to the conclusion that their constitution may be represented by the formula
3FeO.P²O⁵ + Fe²O³.PO⁵ + 15 aq.
"They belong to the monoclinic system of crystallography, and are of greenish-blue colour, becoming darker gradually on exposure to air."
In several places, when digging below the level of the log pavement and thrusting a staff a few feet downwards, gas bubbled up through the water, which, on applying a lighted match, ignited with considerable explosion. This, on analysis, was found to be carburetted hydrogen or marsh gas, with a small quantity of carbonic acid gas.
Before the stuff inside the circular trench was completely cleared away down to the level of the log pavement, our operations had to be abandoned on account of the severity of the weather. Meantime I drew up the above report from a careful journal kept of each day's proceedings and finds, and at the March meeting communicated it to the Society of Antiquaries of Scotland. But, notwithstanding the great variety of relics discovered, and the important information regarding the general structure of the crannog which had been ascertained, there were still several points requiring further elucidation. Of these the following four were the chief, which may be thus succinctly stated:—
Firstly.—From a perusal of the Plan (Plate II.) it will be observed that at the south side there is at least one well-marked circular group of upright piles external to the one surrounding the log pavement; hence the question which pressed for solution was—Whether these groups merged into the one on the north side, or whether there was another corresponding to the former still further out?
Secondly.—It was obvious that the island extended considerably beyond our original circular trench, so that a correct estimate of it could not be formed from our present data.