I have described the Skerryvore light in the previous chapter; but nineteen and a half miles to the south-east of the latter is another reef, just as exposed, which is as perilous in every respect. Indeed, it may be said to constitute a greater menace to the navigation of these waters, since it lies in the cross-roads of the entrance to the Irish Channel, the Firth of the Clyde, and the Minches. A powerful light mounts guard on the Rhins of Islay, twenty-seven miles due south, but between the latter and Skerryvore there are forty-three miles of coast, as dangerous as the mariner could wish to avoid, with this rock looming up almost halfway. This peril is the Dhu-Heartach, lying out to sea in deep water, fourteen miles from the nearest point of the mainland. The physical configuration of the sea-bed at this point is somewhat similar to that prevailing at Skerryvore. The Ross of Mull tumbles abruptly into the Atlantic, to reappear out to sea in the form of the Torrin Rocks, which run for a distance of four and a half miles in the direction of Dhu-Heartach. Then the reef comes to a sudden stop, to be seen once more, nine miles farther out, in the rounded hump of Dhu-Heartach, this being practically the outermost point of the ridge. Being so isolated and projecting so suddenly from deep water, this ledge claimed many victims among the vessels frequenting these unlighted waters. The Commissioners of Northern Lighthouses were assailed for not marking the danger spot in some form or other. The authorities, however, were fully alive to the need of such protection, but it was not until 1867 that they were able to proceed with the erection of a lighthouse. The situation is peculiar, and the engineers, Messrs. D. and T. Stevenson, were faced with a somewhat perplexing problem recalling those which had arisen in conjunction with the Skerryvore, not far distant. Indeed, the Dhu-Heartach undertaking might very well be described as a repetition of those struggles, with a few more difficulties of a different character thrown in. The rock itself in reality is a series of islets, or hummocks, surrounding the main hump, which is 240 feet in length by 130 feet in breadth, the highest point of the rounded top being 35 feet above high-water at ordinary spring-tides. On all sides the lead marks very deep water, the result being that in times of storm and tempest the rollers of the Atlantic, having a “fetch” of some 3,000 miles or more, thunder upon it with terrific force, the broken water leaping high into the air. It is very seldom that the rock can be approached even in a small boat and with a calm sea, as the hump is invariably encircled in a scarf of ugly surf. The swell strikes the western face of the rock, is divided, flows round the northern and southern ends of the obstruction, and reunites on the eastern side. Consequently the rock is nearly always a centre of disturbance.