Autobiography of Sir John Rennie, F.R.S. 21

Autobiography of Sir John Rennie, F.R.S. 21

On the Mediterranean the entrance to the canal is protected by an

artificial harbour composed of two piers carried from the shore. The

western pier is carried out 2400 yards in a straight line, pointing

towards the north, it then inclines slightly to the east for 330 yards,

so that the total length of the west breakwater or pier is 2730 yards, or

8190 feet. The eastern breakwater or pier is carried out from the shore

at a distance of 1530 yards from the commencement of the western pier,

and is extended in a northerly direction 2070 yards, where it terminates

at 760 yards from extremity of the west pier, which constitutes the

entrance. Thus the two piers enclose a space of 500 acres, with a depth

within of 26 feet. This harbour is said to be well protected against the

prevailing or north-west winds.

 

This outer harbour, called Port Said, is connected with extensive quays

and basins within, from whence the canal proceeds across the isthmus.

At 52 miles from Port Said there is Lake Timsah; also Lake Ismaila and

the Bitter Lakes, at 57 miles from Port Said. These Bitter Lakes cover

a surface of about 100,000 acres, and will always ensure a considerable

draught or current from the Red Sea, to compensate for the large amount

of evaporation which is constantly going on, particularly during the

summer season, and is said to amount to about 250,000,000 cubic feet

daily. In order to supply fresh water to Suez, Ismaila, and Port Said, a

considerable channel has been made from the Nile, at Cairo, to Suez and

Ismaila, and a double line of cast-iron pipes between Ismaila and Port

Said, with pumping engines of the requisite power at the former place.

 

The entrance to the Suez end of the canal is formed by an extensive

double embankment through the shoal water, increasing gradually from a

width of 72 feet at bottom, to 980 feet, where there is an open tidal

dock, with 26 feet depth at low water.

 

This is no doubt a very extraordinary performance, rendered remarkable

for the vast amount of capital which has been raised by a single

individual--not an engineer--and the wonderful energy and perseverance

with which he has accomplished it, opposed by innumerable obstacles,

political and financial, which would have daunted and overwhelmed any

person of ordinary physical powers. Although as an engineering work it

is encountered by no unusual difficulties in the execution--being simply

a matter of digging and dredging upon a vast scale--yet it certainly

entitles M. Lesseps and his officers to _the greatest credit_.

 

Having now generally described the canal, let us consider how far natural

obstacles exist which should cause any doubts as to its being possible

to maintain the canal at such an expense as will enable it to produce

something like a reasonable profit upon the capital expended in making it.

 

These obstacles may be enumerated as follows:

 

Firstly. The alluvial matter brought down by the Nile, and that from the

prevailing littoral westerly current in the Mediterranean.

 

Secondly. The sands driven by the north-westerly winds into Port Said.

 

Thirdly. The sands driven into Suez by the southerly winds.

 

Fourthly. The sands driven into the canal from the surrounding deserts by

the kamsin, or south-east winds.

 

Fifthly. From the great evaporation which will take place, and the

consequent requirement of a corresponding supply of water both from the

Mediterranean and the Red Sea.

 

Sixthly. Whether the expenses which must necessarily be incurred in

overcoming these obstacles will amount to such a sum as will render the

canal practically useless, that is to say, that it will not be worth the

while of the Company to maintain it.

 

Before considering these important questions, it will be right to

investigate the natural causes which have formed the Isthmus of Suez.

I think we may conclude that Africa was originally an island, and that

by degrees the waters of the Red Sea, driven in by the southerly winds,

and those of the Mediterranean, driven by the northerly winds, brought

with them a great quantity of alluvial matter; at the junction of these

waters the currents would be destroyed, and the alluvium with which the

waters were charged would be deposited and form a bank or bar, which by

degrees rose above the ordinary level of the sea. This bank, once formed,

would continually increase, not only from the alluvium brought in by the

seas, but also from the sands blown in by the northerly and southerly

winds from the surrounding deserts; and thus, in the process of time, the

present isthmus would be formed. I think that the practical evidence of

this is undoubted. The same operations are still in existence, and it is

simply a question of time as to the increase.

 

Having discussed the cause of the formation of the isthmus, I will now

proceed to consider the objections or obstacles above mentioned. With

regard to the first, the waters of the Nile are constantly bringing down

alluvial matter, but whether the quantity brought down now is the same as

formerly, or greater or less, is a question which nothing but experience

can decide. But as far as experiments have already been made, it appears

that the accumulation which has already taken place is considerable, and

if it proceeds in the same ratio as hitherto, it must shortly become a

very serious question whether it should be removed or not, and whether it

might not be remunerative to do so.

 

Secondly. With regard to the sands driven in by the northerly winds;

these must be very considerable, and not being able to escape, they

must accumulate and tend to fill up the harbour; this will necessitate

constant dredging to keep it open.

 

Thirdly. The sands driven by the tide and the southerly winds into the

Suez end of the canal. These also must be very considerable, as is

already evinced by the great extent of shallow water at the northern

extremity of the Red Sea. This also must be reduced by dredging.

 

Fourthly. With regard to the quantity of sand which may be expected to be

driven into the other parts of the canal from the surrounding deserts,

during the winter and spring prevailing kamsin, or southeasterly gales.

This quantity has been proved by one year’s experience to be not less

than 310,000 cubic yards, and at times it may possibly be much more. It

is proposed to check this by planting the sides of the canal with trees.

Still a great deal of dredging must be constantly required.

 

Fifthly. The evaporation from the Bitter Lakes, and parts of the canal

adjacent, is said to be 250,000,000 cubic feet of water, which is

equivalent to about three-quarters of an inch daily. This water will have

to be supplied chiefly from the Red Sea; and as it will have to pass

through such a narrow channel, the velocity of the current will probably

amount to two or three miles per hour, and if the banks of the canal

are not well secured by paving, or similar works, they will be liable

to be seriously affected. The constant indraught of the current will

impede vessels coming from the Mediterranean, whilst it will facilitate

the passage of vessels coming from the Red Sea; and in the same manner

there will be a constant current from the Mediterranean, but by no means

to so great an extent. These currents will also very probably bring

in a considerable quantity of alluvium. They will not, however, very

materially interfere with the passage of steam-vessels, although, if the

latter are permitted to go at full speed, the waves produced by them will

scour away the sides considerably, unless well protected by stone paving,

fagoting, or similar works.

 

Upon the whole, viewing the difficulties above mentioned, the question

naturally arises, whether they are of such a character as to be

insurmountable; and to this I think we may safely say that they are

not. What has been done once, as has been proved by the completion of

the canal, can be done again, and will be maintained with much less

difficulty. So far, therefore, viewed simply as a work of engineering,

it resolves itself into a question of cost, or in other words, will

the work pay as a commercial speculation, seeing that it has already

cost 20,000,000_l._, and a great deal more is still required before it

can be said to be quite complete, besides a very large sum for annual

maintenance, and what this last item will be it is very difficult to

decide, and nothing but experience can prove; still the more the canal

becomes known, the more in all probability will it be used, and therefore

the more money will be available for keeping it in repair. In addition to

the dredging, it is very probable that the piers, both at Port Said and

Suez, will have to be extended considerably.

 

The whole of the valley of the Nile, from the head of the delta below

Cairo, is bordered by ridges of sandstone hills a few hundred feet

high, with generally a plain monotonous tableland above, intersected by

numerous ravines; no granite appears until we reach Assouan. In the

vicinity of this place there are numerous quarries of fine granite,

chiefly red; the masses are so compact that blocks of almost any size may

be obtained from near the surface. From this district all the granite for

the obelisks, statues, and columns of the various buildings, temples,

and pyramids on both sides of the valley have been taken. Transported

in flat-bottomed boats and rafts to the places where they were intended

to be used, they were landed by means of inclined planes of wood, with

rollers, and wedges, assisted by numerous rough capstans or windlasses,

worked by countless gangs of men. This work appears to have been done

with considerable skill, and the necessary combined operations were

carried on simultaneously, by means of well-concerted signals. These

operations are very clearly explained by the sculptured figures, and have

been published by Sir Gardner Wilkinson and others.

 

Whilst examining the granite quarries near Assouan, I observed several

imperfect blocks, which the Egyptians had commenced quarrying, but found

them defective, and ceased working them. The mode of quarrying seems to

have been nearly the same as we employ at the present time, namely, by

wedges, levers, and pickaxes. Even if gunpowder had been known it would

have been of very little use, for it would have in most cases destroyed

the blocks, and the waste would have been enormous.

 

It does not quite clearly appear of what metal the tools were composed

with which they worked the granite, whether of iron or bronze; if of the

former, it must have been case-hardened. The polishing would be done by

attrition with emery or sharp silicious sand. As for the stone, being

sandstone, it was easily worked, and softer tools only were required.

 

As soon as I got back to Alexandria my first inquiries were for poor

Demetrius. To my great delight I found him quite recovered, and

overjoyed at seeing me; but he said he had been very ill for six weeks,

and had several times considered himself dying. I immediately set to

work making arrangements for my journey overland to Palestine, when

I was suddenly interrupted by letters from my father, saying that he

was very unwell, and wishing me to come back as soon as possible. I

instantly dismissed Demetrius with a very handsome gratuity, discontinued