[footnote] *See, generally my 'Essai sur la Geographie des Plantes, et le Tableau physique des Regions Equinoxiales', 1807, p. 80-88. On the diurnal and nocturnal variations of temperature, see Plate 9 of my 'Atlas Geogr. et Phys. du Nouveau Continent'; and the Tables in my work, entitled 'De distributione Geographica Plantarum, secundum coeli tempriem, et altitudinem Montium', 1817, p. 90-116; the meteorological portion of my 'Asie Centrale', t. iii., p. 212, 224; and, finally, the more recent and far more exact exposition of the variations of temperature experienced in correspondence with the increase of altitude on the chain of the Andes, given in Boussingault's Memoir, 'Sur la profondeur a laquelle on trouve, sous les Tropiques, la couche de Temperature Invariable.' (Ann. de Chimie et de Physique, 1833, t. liii., p. 225-247.) This treatise contains the elevations of 128 points, included between the level of the sea and the declivity of the Antisana (17,900 feet), as well as the mean temperature of the atmosphere, which varies with the height between 81 degrees and 35 degrees F. The regions of the torrid zone not only give rise to the most powerful impressions by their organic richness and their abundant fertility, but they likewise afford the inestimable advantage of revealing to man, by the uniformity of the variations of the atmosphere and the development of vital forces, and by the contrasts of climate and vegetation exhibited at the different elevations, the invariability of the laws that regulate the course of the heavenly bodies, reflected, as it were, in terrestrial phenomena. Let us dwell, then, for a few moments, on the proofs of this regularity, which is such that it may be submitted to numerical calculation and computation.