From this circumstance the Doctor derives a new proof that the sand-hills have travelled from the southward; and in further proof of the non-existence of any chain of hills in this quarter, he has instanced the passage of northerly winds from the Mediterranean, to find their equilibrium in the southern regions of Africa; which passage they could not have effected, he supposes, if they had had a chain of hills to get over in their journey! The Doctor then proceeds to relate the expedition of the Psylli, as recorded by Herodotus, in further support of his position[6]; but in telling us that when these unfortunate gentlemen arrived on the confines of the desert, they were all of them buried in the sands which there assailed them, he does not express the surprise which might be expected at their not having met with a similar accident long before they arrived at that point; for this misfortune might assuredly have happened with equal probability before they set out on their journey to the southward, if the whole of the country, as we are informed by the Doctor, consisted of nothing else, from the desert to the sea, but the formidable red sand which at last put an end to them. The fact is, however, that the “ampia depressione” which is stated by Signor Della Cella to exist between the bottom of the gulf and the great desert, is unfortunately interrupted by a chain of hills, a little inland, of at least four or five hundred feet in height; and we will venture to assert that, in the whole of the tract which has here been described by the Doctor, there is no part where high land does not intervene between the sand-hills and the desert alluded to. We are sorry to place so substantial an impediment in the way of the northerly wind, which the Doctor imagines could not go to the southward to gain its equilibrium if such a bar were placed in its route; but if the whole country from the sea to the Niger were never again to be refreshed with this desirable breeze, we must still be obliged to leave our hills where we saw them in spite of so severe a misfortune. In stating that the level supposed to exist between the bottom of the Gulf of Syrtis and the great desert is not uninterrupted by hills, we must also observe that these hills are not of sand, and that a great portion of marshy and stony land is mingled with the sand which the Doctor states to be exclusively found there. We must at the same time remark, that the only part where the sand is red is in the neighbourhood of the sulphur mines; and this peculiarity may be considered as wholly occasioned by the nature of the soil where it is found. It is besides of so fine a texture as to partake more of the nature of dust than of desert sand, which is neither so red nor so light. It is not raised up in large heaps like the sand on the beach, but scattered over the surface in little hillocks, on which a scanty vegetation is occasionally observable. In fact this substance has no resemblance