During the years 1895–6 the late H. Swainson Cowper visited the Tarhuna pleateau of Tripolitania and examined in considerable detail a large number of ancient sites. The results of this exploration, first published in the Antiquary, were later embodied in a monograph published in 1897. Cowper was not the first European to visit the ancient monuments of the Tarhuna region: he had been preceded by Smyth (1817), Barth (1850), Von Bary (1875), and Rohlfs (1879). His own work was more detailed, and geographically more concentrated, than that of his predecessors, and his publication, amply illustrated by photographs and drawings, remains to-day an indispensable companion for any investigator of ancient sites in the eastern Gebel.
Cowper's main thesis, which occupies a predominant place in his book, was that the trilithon-shaped ‘senams’ (arabic for ‘idols’) of the Tarhuna plateau were prehistoric monuments of a religious character. This conclusion was immediately challenged by Sir John Myres and the late Sir Arthur Evans, who demonstrated conclusively that these megalithic structures were in fact the frames of Roman olive-presses. In consequence general interest in the Tarhuna plateau declined, and even the researches of De Mathuisieulx (1901–4), which resulted in the discovery of the important neo Punic inscription of Ras el-Haddagia, failed to counterbalance the lost repute of the ‘senams’.