ANNOTATIONS AND ADDITIONS. 451 



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 form- 

 ation 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 Di- 

 reccion 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 Grolfo de San Miguel, into which the Rio Tuyra 

 falls, with its tributary river the Chuchunque (Chuehunaque). 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 con- 

 siderable 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 obser- 

 vations), 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 particu- 

 larly 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 



