Page:Popular Science Monthly Volume 67.djvu/237

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A FEW weeks ago the Springfield Republican published the following extract from a letter sent by our minister to Costa Rica, Hon. W. L. Merry, to Gen. G. W. Davis, governor of the Panama canal zone:

Six years and a half of residing in San José have made manifest to me its fine and agreeable climate. When this fact will be known to the many American officials and employees coming to the Isthmus of Panama to work under the canal commission, they will take advantage of the opportunity to visit Costa Rica for recreation and for their health. . . . A few weeks stay here would invigorate our men.

The writer spent six years, from 1889 to 1895, on the Central American plateau and gathered some meteorological and physiological data which led him to the conviction that our minister's statement is not exaggerated. The climate of that portion of the upland which extends from the Panama isthmus to the Yucatan peninsula, and which includes the highlands of Costa Rica, Nicaragua, Honduras and San Salvador, has features of its own, not frequently found under the tropics and never outside of them.

The uniformity of temperature throughout the year, which characterizes the tropical climate, an altitude of some 1,000 feet above sea level, with its corresponding decrease in the density of air, a lower temperature than could be expected for such an altitude in the torrid zone, are the main features of the climate of the Central American plateau. The last of these is the most important. The value of tropical plateaus as health resorts is a subject which has been much discussed recently. That of the Central American upland will be better understood if some of the conclusions which have been reached within the last ten years, as well as some of the experiments which have led to these conclusions, are previously stated.

The density of air decreases rapidly as one rises on a mountain slope. At an altitude of 18,500 feet, a given volume of air contains but one half the quantity of oxygen which it contains at sea-level. Scarcity of oxygen does not seem to be a desirable condition, yet recent experiments have shown that, within certain limits, that very quality of mountain air induces in the human system changes which