General Bolivar at my request caused an exact levelling of the Isthmus between Panama and the mouth of the Rio Chagres to be made in 1828 and 1829 by Lloyd and Falmarc. (Philosophical Transactions of the Royal Society of London for the year 1830, p. 59-68.) Other measurements have since been executed by accomplished and experienced French engineers, and projects have been formed for canals and railways with locks and tunnels, but always in the direction of a meridian between Portobello and Panama,—or more to the west, towards Chagres and Cruces. Thus the most important points of the eastern and south-eastern part of the Isthmus have remained unexamined on both shores! So long as this part is not examined geographically by means of exact but easily obtained determinations of latitude and of longitude by chronometers, as well as hypsometrically in the conformation of the surface by barometric measurements of elevation,—so long I consider that the statement I have repeatedly made, and which I now repeat in 1849, will still be true; viz. “that it is as yet unproved and quite premature to pronounce that the Isthmus does not admit of the formation of an Oceanic Canal (i. e. a canal with fewer locks than the Caledonian Canal) permitting at all seasons the passage of the same sea-going ships between New York and Liverpool on the one hand, and Chili and California on the other.”
On the Atlantic side (according to examinations which the Direccion of the Deposito hidrografico of Madrid have entered on their maps since 1809) the Ensenada de Mandinga penetrates so deeply towards the south that it appears to be only four or five German geographical miles, fifteen to an equatorial degree, (i. e. 16 or 20 English geographical miles), from the coast of the Pacific on the east of Panama. On the Pacific side the isthmus is almost equally indented by the deep Golfo de San Miguel, into which the Rio Tuyra falls, with its tributary river the Chuchunque (Chuchunaque). This last-named stream in the upper part of its course approaches within 16 English geographical miles of the Atlantic side of the isthmus to the west of Cape Tiburon. For more than twenty years I have had inquiries made from me on the subject of the problem of the Isthmus of Panama, by associations desirous of employing considerable pecuniary means: but the simple advice which I have given has never been followed. Every scientifically educated engineer knows that between the tropics, (even without corresponding observations), good barometric measurements (the horary variations being taken into account) afford results which are well assured to less than from 70 to 90 French or 75 to 96 English feet. It would besides be easy to establish for a few months on the two shores two fixed corresponding barometric stations, and to compare repeatedly the portable instruments employed in preliminary levelling, with each other and with those at the fixed stations. Let that part be particularly examined where, near the continent of South America, the separating mountain ridge sinks into hills. Seeing the importance of the subject to the great commerce of the world, the research ought not, as hitherto, to be restricted to a limited field. A great and comprehensive work, which shall include the whole eastern part of the Isthmus,—and which will be equally useful for every possible kind of operation or construction,—for canal, or for railway,—can alone decide the much discussed problem either affirmatively or negatively. That will be done at last, which should, and, had my advice been taken, would have been done in the first instance.
[59] p. 300.—“That which is awakened in us by childish impressions or by the circumstances of life.”
On the incitements to the study of nature, compare Kosmos, Bd. ii. S. 5, (English edit. vol. ii. p. 5).
[60] p. 302.—“Of importance for the exact determination of the longitude of Lima.”
At the period of my Expedition, the Longitude of Lima was given in the maps published in the Deposito hidrografico de Madrid, from the observations of Malaspina, which made it 5h. 16m. 53s. from Paris. The transit of Mercury over the Sun’s disk on the 9th of November, 1802, which I observed at Callao, the Port of Lima, (in the northern Torreon del Fuerte de San Felipe) gave for Callao by the mean of the contact of both limbs 5h. 18m. 16s. 5, and by the exterior contact only 5h. 18m. 18s. (79° 34´ 30´´). This result (obtained from the Transit of Mercury) is confirmed by those of Lartigue, Duperrey, and Captain FitzRoy in the Expedition of the Adventure and Beagle. Lartigue found Callao 5h. 17m. 58s., Duperrey 5h. 18m. 16s., and FitzRoy 5h. 18m. 15s. (all West of Paris). As I determined the difference of longitude between Callao and the Convent de San Juan de Dios at Lima by carrying chronometers between them four times, the observation of the transit of Mercury gives the longitude of Lima 5h. 17m. 51s. (79° 27´ 45´´ W. from Paris, or 77° 06´ 03´´ W. from Greenwich). Compare my Recueil d’observations astron. Vol. ii. p. 397, 419 and 428, with my Relat. hist. T. iii. p. 592.
Potsdam, June 1849.
GENERAL SUMMARY
OF THE
CONTENTS OF THE SECOND VOLUME.
Physiognomy of Plants—p. [1] to p. [31].
Universal profuse distribution of organic life on the declivities of the highest mountains, on the ocean, and in the atmosphere. Subterranean Flora. Siliceous-shelled Polygastrica in masses of polar ice. Podurellæ in tubular holes in the glaciers of the Alps; the glacier flea (Desoria glacialis). Small organic creatures in the dust which falls like rain in the neighbourhood of the African Desert [3]-[8]