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Show ANNOTATIONS A.ND ADDITIONS. 451 in 1 49, 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 1 09), 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 |
