A History of Art in Sardinia and Jud.ea. & m M 1 l" 1 '
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,' i^ 1 1 J%jiq in the centre, like the miners of the Mont Cenis tunnel. Without the mariner's compass to guide them, or adequate knowledge for taking plans, elevations, sections, etc., they rapidly diverged to one side (Fig. 2 1 6). The men from the Siloam end became aware that they had not been going straight ; as here the rocky crust overhead was not thick, they made a shaft up to the surface, when they perceived that they had rapidly drifted to the east (Fig. 218). After having ascertained this they ran straight for some time, following the rock contour, or perhaps a particular seam of rock. One might be inclined to think that some 70 metres further they again began to make another shaft, but that the difficulty of getting to the crest of the hill, which here is of considerable height, caused them to leave it un- finished. This may also have been due to the sound of the picks in the other tunnel, which was likely to be heard at a great distance through the soft strata ; but even then their course betrays great uncertainty ; and at the points i, h, g (Fig. 219), certain "set backs " in the walls of the passage indicate sudden change of direction on the part of the excavators. In the directions which are indicated by the headings at a and f, the two gangs were working almost parallel one to the other, and might have passed each other without joining, having a thick- ness of seven feet of rock between — those in the up-stream tunnel being
