To give still greater facility and more security to the operations of the engineers, His Highness the viceroy, who had generously provided for all the requirements of the expedition, condescended to make choice of one of us to direct the whole of the operations, with the assistance of a brigade of Egyptian Engineers and a Company of artillerymen, who assisted in all the operations of levelling and verification.
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.
| STATIONS | Taken from low water in the Mediterranean at Tineh. | Variation from the Levels of 1847. | |
|---|---|---|---|
| 1853. | 1847. | ||
| Low water in the Mediterranean at Tineh. | 0 m. 0000 | 0 m. 0000 | 0 m. 0000 |
| Stations of the German Engineers at Tineh. | 1 m. 5586 | 1 m. 7400 | 0 m. 1814 |
| Station at the Staff 29 L. 1853, point 26 of Bourdaloue’s triangulation of the most elevated Lagoons of Lake Menzaleh at Ras el Ballah. | 1 m. 9800 | 1 m. 9800 | 0 m. 0000 |
| Station 4 L. 1853, Bourdaloue’s point A, which was found and verified. | 7 m. 8210 | 7 m. 4300 | 0 m. 3910 |
| Bourdaloue’s Station Staff at the mouth of the Canal (this staff is not certain). | 3 m. 8280 | 3 m. 0800 | 0 m. 7480 |
| Station 3 L. 1853, at the Serapeum, or Bourdaloue’s No. 83. | 16 m. 5950 | 16 m. 2300 | 0 m. 3650 |
| Upon the most elevated deposits in the basin of the Isthmus. | 2 m. 4100 | —— | —— |
| 2 m. 0300 | —— | —— | |
| 1 m. 8600 | 1 m. 8000 | 0 m. 0600 | |
| Station 2 L. 1853, and Bourdaloue’s Station B. 30, on a block of petrified wood, covered with sandy secretions, placed upon the deposits in the basin of the Isthmus. | 2 m. 4380 | 2 m. 1100 | 0 m. 3280 |
| Station 1 L. 1853, at the Persepolitan monument, upon a block of sandstone, south of the Bourdaloue excavations. | 11 m. 6300 | 11 m. 3700 | 0 m. 2600 |
| Station on the Caravan Road, at the Staff Station, 3 L. 1853. | 2 m. 3900 | —— | —— |
| Station at the staff at the starting point No. 1, L. 1853. | 1 m. 5186 | —— | —— |
| Station on the quay of the Suez hotel, the same as that of M. Bourdaloue. | 2 m. 4286 | 2 m. 6100 | 0 m. 1814 |
The most striking fact to be observed in the examination of this table is, the slight relief of the ground above high water of the Red Sea, in the whole extent of the Isthmus. There are only two points somewhat elevated. The first, proceeding from Suez, is met with before Lake Timsah, and is that which we shall call the Serapeum bar; its greatest elevation is 16 met., 5950, above low water in the Mediterranean. The second point is at the outlet of the lake, and its greatest elevation is fifteen metres, at the spot known as the bar of El Guisr; but the line of the Canal may be carried in a direction where but ten metres are met with for some kilometres of length. Supposing therefore the bed of the canal to be established at the depth of 6 met., 50, below low water in the Mediterranean, the greatest excavation would be at the bar of El Guisr, and would show a total depth of 16 met., 50, which is nothing extraordinary; supposing it even twenty metres, the requisite excavation would bear no comparison with what was executed in Mexico, during the Spanish occupation. For, in their then difficult position, and in the absence of tools and improved means, the Spaniards were able to effect, near the town of Mexico, which was threatened with invasion by the waters of the neighbouring lakes, the cutting of Huehuetoca, the total length of which is 20,585 metres, and its depth from forty-five to sixty metres, for a length of more than 800 metres, and from thirty to fifty metres for a length of 3500 metres. And yet the expense of this work was only 31,000,000 francs.
The levelling also shows, that by adopting 6 met., 50, for the bed of the Canal, there will be a length of 18 kil. in the Bitter Lakes, where there will not be a shovelful to remove, and for another 18 kil. there will be very little to do; and as these lakes are dry at a depth of 8 met., 39, below low water, all the earth-works for the whole length of them could be performed in the dry, if found advantageous to do so.