The artificial curiosities are very numerous, and claim the attention of all who may visit this country. They ought properly to be divided into two classes; in the first of which may be placed the subterraneous cavern and passage near Tangiers; the ruins of the amphitheatres, triumphal arches, temples, &c. erected by the Carthaginians, Romans, and Arabs, at Fez and the several other towns of Barbary. The country is besides all over scattered with the remains of ditches and ramparts, evidently designed for the defence of camps, forts, and castles, no other vestiges of which, however, can be found. Besides these, I have observed a number of round towers, which appear to have belonged, some to houses of religion, and others to the palaces or residences of former rulers in this country. In the second class, we may place the efforts of the architectural and mechanical genius of the present inhabitants, exemplified in the wonderful aqueducts at Morocco, which commence in Mount Atlas (by the natives called _Gibbel-el-Hadith_), and convey water in the greatest abundance to all the houses of the city and its environs. Nor is the wheel at Fez, which I mentioned in a former letter, less worthy of remark; and several mausoleums in their burial-places have been constructed in a very costly style, the stucco of the walls being remarkably smooth and beautiful, and as hard as marble; but these tombs are exceptions to the general rule; for, as I have before observed, the greater part are but rude buildings. There are many other curiosities, which to describe minutely would fill a volume. LETTER XX. _Practice of Physic--Astrology--Poetry--Entertainment given by the Author to the Moors--Their Astonishment at the Effects of Electricity_. Mequinez. I shall now speak of their principal or rather only studies, which are, physic, astrology, and poetry. First then of physic, to give you an accurate idea of the extent of their knowledge in which, it will be sufficient to describe their practice of it; and I am sure you, my dear D----, and every other friend to humanity, will agree with me, that it would have been better for their countrymen if they had never attempted it at all, as unassisted nature would do more, for those afflicted with disease, than such bunglers.