9. At North Erradale; "pans" broken up. Mr Macadam states that a heavy sample of bog iron from this place yields 49 per cent., and a sandy portion 38¾ per cent. of metallic iron.
10. At South Erradale. There is a fence wall, locally called Garadh Iaruinn, or the "iron dyke," entirely composed (for fifty yards of its length) of masses of bog iron, varying from 3 to 13 inches in thickness, and some of them nearly a yard in length. The dyke was erected in 1845, when the present system of crofts was being established in Gairloch. Quantities of bog iron are also to be seen in other dykes, and the soil of probably about two acres of the adjacent cultivated land mainly consists of comminuted bog iron. There must have been large deposits of it at this place; one or two unbroken masses still remain in situ. Mr Macadam finds that the heavier kind yields, on analysis, 50 per cent. of metallic iron, whilst a sandy portion contains 46½ per cent.
11. On the farm of Point, Gairloch, near the house of Mr MacClymont, farmer. The heavy bog iron analysed by Mr Macadam yields 50 per cent. of metallic iron, and some red sand from the same place contains 15 per cent.
II.—At the Historic Ironworks.
Mr Macadam is of opinion that bog iron was not only used at the ancient bloomeries, but also at some of the historic furnaces in Gairloch parish, particularly at Letterewe and Talladale. He gathers this from the general character and composition of some of the slags found at these places. It was in the early stage of Sir George Hay's career as a manufacturer of iron that he used the native bog iron ore; later on he began to import iron ores of a different kind from other parts of the kingdom,—at first in order to mix them with the local bog iron, and afterwards, perhaps, for separate use. The introduction of these imported ores may have been primarily due to the failure of the supply of the bog iron; it undoubtedly led to a vast improvement in the results obtained at Sir George Hay's furnaces.
The evidence that Sir George imported what we may term foreign ores is not far to seek.
At the Letterewe ironworks there are to be seen fragments of two kinds of imported iron ore, scattered in the soil of the field adjoining the furnace, or built into fence walls; they are red hematite ore, and clayband ironstone.
Mr J. E. Marr, F.G.S., has described these foreign ores as follows:—"Red hematite exactly the same as that in the Furness and Whitehaven districts in England. Large masses of a brown clay ironstone; one of these masses being a septarian nodule, with radiating crystals along the cracks; the other being bedded, and containing numerous plant and fish remains, but no shells; these fossils shew them to belong to the carboniferous system."
Some small fragments of similar clay ironstone have been found on the traditional site of the Talladale iron furnace.
On the bank above the ironworks on the river Ewe, called the Red Smiddy, are fragments of clayband ironstone, which Mr Marr has described as follows:—"Clay ironstone nodules, mostly blue inside, and weathering red and yellow on the outside. Many of these were septarian; and when fossils occurred they were of shells, and there were no traces of plants or of fish remains. This ore, in fact, is entirely different from either of the two kinds found at the Letterewe furnace. At the same time, the fossils shew that it also belongs to the carboniferous system."