The coolness of the climate is occasioned by the wind and a peculiar state of the atmosphere. The wind generally blows from different points of the compass between the south west and the south east. When from the former direction, it crosses in its course a great portion of the Pacific Ocean, and when it comes from the eastward it has not to pass over sandy deserts or scorching plains, but to traverse first the immense tract of woodland countries lying between the Brazils and Peru, and afterwards the frozen tops of the Cordillera, at a distance of twenty leagues from Lima; so that, in both cases, it is equally cool and refreshing. A northerly wind is very seldom felt in Lima; but when it blows, as if by accident, from that quarter, the heat is rather oppressive. On the 6th of March, 1811, the wind being from the north, I made the following observations with a Farenheit's thermometer, at one o'clock, p. m.
| In the shade in an open room | 80° |
| In the air, five yards from the sun's rays | 87° |
| In the sun | 106° |
| Water in the shade from sunrise | 74° |
| Water in a well 20 yards below the surface of the earth | 70° |
| Sea water at Callao at 4 p. m. | 64° |
| Heat of the body, perspiring | 96° |
| ———————after cooling in the shade | 94° |
The heat of the sun in summer is mitigated by a canopy of clouds, which constantly hang over Lima, and although not perceptible from the city, yet when seen from an elevated situation in the mountains, they appear somewhat like the smoke floating in the atmosphere of large towns where coal is burnt; but as this material is not used in Lima, the cause and effect must be different.
If I may be allowed to give an opinion different from that of several eminent persons who have written on the climate of Lima, it is, that the vapours which rise on the coast or from the sea are lifted to a sufficient height by the action of the sun's rays to be caught by the current of wind from the southward and westward, and carried by them into the interior; whilst the exhalations from the city and its suburbs only rise to a lower region, and are not acted upon by the wind, but remain in a quiescent state of perfect equilibrium, hanging over the city during the day, and becoming condensed by the coolness of the night, when they are precipitated in the form of dew, which is always observable in the morning on the herbage.
Lima may be justly said to enjoy one of the most delightful climates in the world; it is a succession of spring and summer, as free from the chills of winter as from the sultry heats of autumn.
Notwithstanding this almost constant equability, some writers have imagined that four seasons are distinguishable. Such persons, however, must undoubtedly have either been endowed with peculiar sensibility, or have been gifted with an amazing philosophy. Not content with the beauties of this climate, some have attached to it the properties which belong to the ultra-tropical countries—jealous perhaps of the theoretical comforts from which they are practically free, and in the full enjoyment of a climate the maximum heat of which seldom exceeds 78° of Farenheit's thermometer, and the minimum of which is seldom below 62°, wishing to perfect it by having the maximum at 100°, and the minimum below zero! Peralta, in his 8th canto, has very quaintly described the beautiful climate of this city:—
"En su orisonte el sol todo es aurora
Eterna, el tiempo todo es primavera
Solo es risa del cielo cada hora
Cada mes solo es cuenta del esfera.
Son cada aliento, un halito de Flora
Cada arroyo una Musa lisongera;
Y los vergeles, que el confin le debé
Nubes fragantes con que el ciclo llueve."
One of the peculiarities of this climate, as well as that of the coast of Peru from Arica to Cape Blanco, being a distance of about 16 degrees of latitude, is, that it can scarcely ever be said to rain. Several theories have been advanced to account for this anomaly of nature. The following facts and explanations will, perhaps, tend to unravel the difficulty.
In April or May the mists, called garuas, begin, and continue with little interruption till November, which period is usually termed the winter solstice. The gentle winds that blow in the morning from the westward, and in the afternoon from the southward, are those which fill the atmosphere with aqueous vapours, forming a very dense cloud or mist; and owing to the obliquity of the rays of the sun during this season the evaporation is not sufficiently rarified or attenuated to enable it to rise above the summits of the adjacent mountains; so that it is limited to the range of flat country lying between the mountains and the sea, which inclines towards the north west. Thus the vapours brought by the general winds are collected over this range of coast, and from the cause above-mentioned cannot pass the tops of the mountains, but remain stationary until the sun returns to the south, when they are elevated by his vertical heat, and pass over the mountains into the interior, where they become condensed, and fall in copious rains. That rain is not formed on the coast from these mists is attributable, first, to a want of contrary winds to agitate and unite the particles, and, secondly, to their proximity to the earth, which they reach in their descent, before a sufficient number of them can coalesce, and form themselves into drops.
The figure of the coast also contributes to the free access of the water that has been cooled at the south pole, on its return to the equatorial regions. From Cape Pilares to latitude 18° the direction of the coast is nearly N. and S.; and from 18° to 5° it runs out to the westward: thus the cold water dashes on the shores, and produces in the atmosphere a coolness that is not experienced in other parts, where the coasts are filled with projecting capes and deep bays; because the current, striking against those, sweeps from the coast, and the water in these becomes heated by the sun, and is deprived by the capes of the current of cold water, excepting what is necessary to maintain the equilibrium, which is diminished by absorption in the bays. The heat increases with astonishing rapidity from latitude 1° south to 10° north; the Gulph of Choco being deprived of the ingress of cooled water from the south by the Cape San Francisco, and from the north by Cape Blanco. The eastern shores of the south Continent of America are much warmer than the western, owing to the great number of capes and bays. The atmosphere does not enjoy the cooling breezes from the pole, which are diverted from a direct course in the same manner as the currents of water, nor the refrigerated winds from the Cordillera.
The southern hemisphere is altogether much cooler than the northern: perhaps in the same ratio that the surface land of the northern hemisphere exceeds that of the southern.
During the months of February and March it sometimes happens that large straggling drops of rain fall about five o'clock in the afternoon. This admits of an easy elucidation. The exhalations from the sea being elevated by the heat of a vertical sun, and impelled by the gentle winds during the day towards the interior and mountainous parts of the country, are sometimes arrested in their progress by a current of air from the eastward, which, having been cooled on its passage over the snow-topped Andes, is colder than the air from the westward; and wherever these currents meet the aqueous particles are condensed, and uniting become too heavy to continue in the upper region of the atmosphere, when they