IS46.] 



THE CIVIL ENGINEEER AND ARCHITECT'S JOURNAL. 



339 



CANAL OF THE ISTHMUS OF PANAMA. 



The following translation of extracts from tiie report of Napoleon Ga- 

 rella, an engineer appointed by the French Government to survey the 

 Isthmus of Panama, is taken from the Journal oj the Franklin Insti- 

 tute: — 



The remarkable isthmus which unites the two Americas and extends 

 between the Gulf of Mexico and (he Pacific Ocean, to a length of 1430 

 miles, in a direction from W'.N.W. to E.S.E., presents along this enormous 

 length a variable width. From the mouth of the Guazacoaico, its point of 

 junction with North America, where it has a width of 137 miles, it con- 

 tinues narrowing regularly enough, with the exception of the two large 

 promontories of Yutacan and Central America, to its other extremiiy, 

 towards the Gulf of Darien, where it is united to South America. It is 

 towards this latter portion, wbere it is called more particularly the Isth- 

 mus of Panama, that it attains its minimum width, trom the mouth ot 

 the Caimito, on tlie Pacific Ocean, to the embouchure of the Uiagres on 

 the Atlantic, the distance is but 30 miles ; but the miuimum width appears 

 to be a little more to the eastward, between (he bay of Mandingo or San 

 Bias, on the Caribbean sea, and the shore of the Pacific Ocean, near the 

 embouchure of the Rio Chepo, where the distance, according to the map, 

 is but 31 miles. The chain of mountains which extends m a direction 

 nearly north and south, the whole length of the two Americas, from the 

 icy seas of the north pole to Cape Horn, presents along nearly its who e 

 length a considerable elevation. Us peaks are only surpassed in height 

 by the summits of the highest of the Himalayas, and even its vast pla- 

 teaux have an elevation superior to that of the highest mountains of the 

 interior of France. This chain extends, without any discontinuity, the 

 whole length of the isthmus, but then as the breadth of the land dimi- 

 nishes, so the ridge of the chain sinks considerably, and presents some de- 

 pressions, of which the height above the ocean is less than that overcome 

 by some of the European canals already constructed. One of these re- 

 markable depressions exists in the neighbourhood of Panama— not at the 

 point where the isthmus is narrowest, but a little to the westward, where, 

 however, it is narrower than at Panama. In examining the configuration 

 of the isthmus from west to east, it will be remarked that, passing from the 

 state of Costa Uica (Central America) into the province of Veraqua (New 

 Granada), under the 85th degree of west longitude, 3 degrees to the west- 

 ward central ridge dividing the waters flowing into the two oceans, ap- 



migueros. The ridge . _ , . .. ., ., • 



Bello, and near the Gulf of San Bias, its previous height. Along this 

 distance there are a number of points whose elevation varies from 425 to 

 525 feet, between which the ridge rises but little, and forms hillocks, and 

 not peaks or elevated masses. This depression of the central chain is, 

 then, one of the first and most evident observations which the explorer 

 makes ; and it has been noticed by nearly all those who have surveyed the 

 isthmus; Mr. Lloyd points it out for the line of a canal ; and it is there, 

 also, that Mr. Morel, the agent of ihe Salomon Company, has laid down 

 his route. It is evidently there that the summit level of the maritime 

 communication to be opened between the two oceans, should be placed. 

 Unfortunately, those who have hitherto visited the isthmus, have only 

 judged approximatively of the height of this portion of the chain, and 

 that by a simple visual observation, made without employing any instru- 

 ment, and mostly at long distances ; and taking, without doubt, as points 

 of comparison, the elevated mountains of the Trinity, and other masses of 

 a considerable elevation, situated more to the eastward ; those of the 

 Cerro Cabra, which are 1614 feet high, and those of the Cerro Grande of 

 Gorgona, which rise to a height of 1017 feet. Thence, doubtlessly, comes 

 the erroneous opinion spread abroad, on the faith of some navigators, that 

 the central chain uniting the elevated table land of iNIexico wiih the Andes 

 of Peru, ceases entirely in the portion of the country of which we are 

 now speaking; and is cut by a transversal valley, where man will have 

 almost nothing to do to establish a navigable coiumunicalion between the 

 two oceans. Thence, also, without doubt, the extraordinary assertion ad- 

 vanced by the Salomon Company, that this depression of the chain oliers a 

 point of passage situated only 37 feet above the mean height of the sea at 

 Panama, a point which the company naturally chose for carrying across 

 the summit level of the canal which they projected. From the sides of 

 the Cerra de la Trinidad flow three principal streams, of which the most 

 important, the Caimito, empties itself into the Pacific 14 miles west of 

 Panama. The two other streams, which flow towards the Atlantic, are 

 the Cano Quebrado and the Rio Trinidad — rising at nearly the same point, 

 they separate as they advance. In the triangular space comprised between 

 them, the laws of nature, which, throughout America, have placed tlie 

 ridge of separation of the waters flowing into the two oceans, nearer the 

 western side, appears to have been maintained. The wide space which 

 separates the bed of the Trinidad from the base of tiie spur, is occupied 

 by vast and, for the most part, unbroken plains, from the middle of which 

 rise some isolated hillocks. One does not there meet with the water- 

 courses which might be expected from their extent, but many s%vamps, and 

 even deep lakes, communicating with the Rio Trinidad by small natural 

 canals, called esteros. In these plains is found the large lake of Vino 

 iinio, observed by Mr. Morel, which is upwards of a league in diameter. 

 Here also are found, near the mouth of the river, the swamps of Agua 



Clara, which have in some places, as I have been assured, a depth of 

 water of 42 feet. 



Besides these streams, there is another on the western slope, flowing 

 directly into the Pacific; it is Ihe Rio Grande, situated between the Cai- 

 mito and Panama, and having its month 1^ miles west of that city. It i« 

 indeed a stream of no great magnitude, the upper portions of which are 

 completely dry during some months of the year; but it presents a charac- 

 teristic which it has in common with other aflluents of the Pacific Ocean, 

 which is, that the lower portion of its bed has but a slight descent and 

 great width, so thai the tide mounts it to a considerable distance, and thus 

 forms an arm of the sea {estero) intruding into the land, with a depth vary- 

 ing from 25 to 33 feet, and sometimes even more, which oflTers facilities for 

 navigation, though only during high water, and as far as the tide flows. 

 It is to this characteristic that the Rio Grande owes its name, though in 

 fact it is but a brook. Alongside of the Rio Grande is another little 

 ravine, pouring its waters directly into the sea. This is the Rio Farvan, 

 having, towards its mouth, a wide and deep bed, which, at this point, is 

 only separated from the Rio Grande by a hill, around which its waters are 

 forced by high tides, flowing into the Alvine marshes, through which the 

 road from Panama to Chorera passes, thus mingling the waters of the two 

 creeks. 



This feature of a great diminution of fall near the embouchure of the 

 stream, is still more perceptible on the Atlantic slope. The Chagres, which 

 is undoubtedly the most important and most voluminous stream of water 

 of this portion of the isthmus, presents it in a very striking manner. The 

 tide of the Atlantic, which rises but from 13 to 15 inches, ascends the 

 river a distance of 17 miles; and is navigable, but with some difficulty, 

 beyond a distance of 18 miles from its mouth. Thence it can be ascended 

 only by poling, on account of the rapidity of the current and the irregu- 

 larity of the bottom. Laden boats ascend it as far as Gorgona and Cruets, 

 but in the dry season (from December to .June) they are obliged to unload 

 the larger barques on a beach near the mouth of the Cano Quebrado, and 

 to load again in smaller boats ; and even with these they have great diffi- 

 culty in reaching Cruets. With the exception of the Rio Chagres, the 

 other rivers of the isthmus can hardly be said to be navigable, and none of 

 them can be made useful for the purposes of navigation. 



The waters flowing from the central chain, at its point of depression, 

 are divided, as we have seen, between two basons : that of the Caimito 

 upon the Pacific slope, and that of the Rio Chagres, or rather of the Cano 

 Quebrado, upon the Atlantic slope. It is then between these two basins, 

 that the point for the passage of a canal of communication between the 

 two oceans, is to be sought. It is along their tributaries that we must 

 look for the valleys where the canal should pass ; and finally, it is in the 

 neighbourhood of the localities where their waters empty into the sea — 

 that is, near the mouths of the rivers Caimito and the Chagres — that we 

 must seek the points of communication of the conal itself with the two 

 oceans; the bars which always form at the points where the running 

 waters of rivers meet the still waters of the ocean, rendering it necessary, 

 as a general rule, to avoid carrying a great line of navigation to those 

 points. 



The Rio Chagres has, in fact, at its mouth, a bar with a depth of water 

 of but 13 feet. Under these circumstances, the insufficiency of such an 

 entrance for an oceanic canal like that of which we are treating, may be 

 easily comprehended ; a canal which should admit ships of the greatest 

 tonnage, and demanding at the least a draft of 23 feet of water. Doubt- 

 lessly it would not be impossible to remedy, at least temporarily, this 

 defect ; but the uncertainty, proved by experience, of the results of ope- 

 rations carried on at the mouths of rivers even larger than the Chagres, 

 especially when they are for the purpose of opposing the accumulation of 

 sand, should induce us to employ such means only in case it should be 

 impossible to find another suitable entrance ; here, however, nature herself 

 appears to have provided one. Five miles to the eastward of the Rio 

 Chagres, is the large and capacious bay of Linion, 21 miles in width, and 

 3| miles long. It has a great depth of water, which, in the centre, reaches 

 32 feet. This bay is separated from the river by a tract of land in general 

 of but slight elevation, and offering some low portions, which aflbrd facili- 

 ties for excavating a canal of communication with the river ; works simple 

 and easily constructed, will suffice for the establishment of a vast and sure 

 port at the entrance of the canal, in the bay, which, opening to the north, 

 is at present exposed directly to the action of the north, north-east, and 

 north-west winds, which reign almost constantly in these latitudes. 



These disadvantages found at the embouchure of Rio Chagres in the 

 Atlantic, are still more apparent at that of the Rio Caimito in the Pacific. 

 This embouchure is situated in the middle of a vast beach, which lovir 

 water leaves uncovered ; it thus unites a want of depth of v\ater and the 

 inconvenience of sand banks. The coast does not olfer in this neighbour- 

 hood a favourable locality for a good port, with a sufficient depth of water, 

 for to the deptli of water necessary for vessels must be added the height of 

 the tide. But, fortunately, the neighbourhood of the port of Taboga, and 

 the almost constant tranquility of the Gulf of Panama, at the bottom of 

 which is the mouth of the Caimito, permit us, in establishing the entrance 

 of the canal, to take into consideration only the depth of water at high 

 tide. 



The place on the coast which appears to me the best to correspond with 

 the required conditions in this respect, is a little bay with an opening of 

 382 yards, situated 24 miles to the eastward of the mouth of the Caimito. 

 At its entrance the mean depth was found to be at least 26^ feet at high 

 tide. There would be but little to do at this point to establish the entrance 



