The general, but non-specialist, opinion upon the Isthmus is not as sanguine as that of Colonel Gorgas upon the hygienic future of the white race in the tropics. The general opinion among Americans seems to be that, as far as they are concerned, they would, if engaged in the tropical parts of South or Central America, avail themselves of the improving means of transit to revisit frequently the United States, and would rely upon such vacations in higher latitudes for the retention of their native vigour. CHAPTER VI ON THE SHORTENING OF DISTANCES BY SEA, AND ON THE STEAMSHIPS AVAILABLE FOR CANAL TRANSIT _The Shortening of Distances by Sea._ AS the sole object of a ship canal is to shorten sea distances, the figures given in this section are of primary importance to a proper understanding of the subject. The figures here given are those for steamships following the actual or prospective routes. They are adopted from the figures supplied to the Canal Commission from the United States Hydrographic Bureau and are expressed in nautical miles. It is perhaps not wholly superfluous to warn the reader that the apparent relative distances as shown on charts of the world, especially those on the usual Mercator projection, are very different from the real relative distances. Moreover, it is impossible to see correctly the relative distances between places far apart on a globe, for the foreshortening of the rounded surface produces distortion. By applying a measuring tape to the globe the true relative distances can be readily ascertained. This is a salutary exercise and serves to correct the erroneous notions which tend to fix themselves in the minds of all of us owing to the appearance of the surface of the globe on the plane of the paper or on the plane of vision. Such a measurement of shortest distances would give a very fair notion of the actual reductions due to the Suez and Panama Canals, but there would still be considerable differences between these figures and the distance calculated from the actual courses pursued by steamships, which in what follows will be referred to simply as "the" distance between ports. [Illustration: RIO GRANDE, NEAR LA BOCA.] [Illustration: RIO GRANDE, FROM ANCON HILL.] The most notable effect of the Panama Canal will be the reduction of distance between the Atlantic and Pacific ports of North America. Taking New York as our port of reckoning on the Atlantic, the distance thence to Panama and all ports north thereof on the Pacific seaboard of Central and North America will be reduced by 8,415 miles. The reduction of distance from New York to the Pacific ports of South America, on the other hand, is not constant, but varies from the above maximum of 8,415 miles at Panama to a minimum of about 1,004 miles at Punta Arenas (in the Straits of Magellan). The _average_ shortening on this coast is therefore 8,415 + 1,004 ------------- = 4,709 miles. 2