M. Talabot, the engineer, in a report published in 1847, has entered into all the details of these operations, and has given an irrefutable proof of the results obtained. As these results differed very widely from those obtained by the engineers of the French expedition, it was difficult to believe in so great an error. M. Sabatier, Consul General of France in Egypt, having been informed of the wish of some learned Frenchmen to have a fresh verification, spontaneously applied to the viceroy of Egypt, and one of us was appointed to undertake it in consequence. The verification was made in 1853. It resulted in favour of the surveyors of 1847. For, the new levels only differ 0 _met._, 1814, from those of 1847, and give as the difference of level between the station on the quay of the hotel at Suez, and low water in the Mediterranean 2 _met._, 4286, instead of 2 _met._, 6100 found by the operations in 1847. There cannot be a moment’s hesitation in making choice between the levellings of 1799 and those of 1847 and 1853, for the two latter were taken under the most favourable circumstances by experienced surveyors provided with the best instruments, and were verified several times without finding any perceptible difference by these various verifications; whilst the levelling of 1799 was undertaken in the midst of the vicissitudes and dangers of warfare, in a hostile country, and in a climate to which the engineers were not accustomed. One part of the operations was performed with the spirit level; another rather important portion could only be done with the water level; the surveyors frequently differed; none of the divisions of these levellings could be verified; and if the last operations had been retarded ever so little, the incidents of the war would have made them impossible; the operations had to be performed with rapidity, and the levels taken in long lengths; with frequent interruptions, and without the check of any verification. This is what M. Lepère has stated in his memorial, where he expresses himself thus:— “Pressed for time, disturbed by the hostile demonstrations of the Arab tribes, frequently obliged to suspend operations, obliged in fine to take a great part of the observations with a water level, with no possibility of making any verification, it is not at all surprising that the able engineers who conducted these operations under such exceptional circumstances should have arrived at uncertain results.” We have therefore adopted the levels taken in 1847 and in 1853, as the only true ones, the only ones that were verified, and the only satisfactory ones. We give an abstract of them in the following table:— STATIONS WITH THE LEVELS TAKEN IN 1853, COMPARED WITH THE LEVELS TAKEN AT THE SAME STATIONS IN 1847.