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NOTES OF A NATURALIST
IN SOUTH AMERICA.
Voyage across the Atlantic-Barbadoes—Jamaica-Isthmus of
Panama-Buenaventura, tropical forest—Guayaquil and the river Guayas-Payta-The rainless zone of PeruVoyage to Callao.
A VOYAGE across the Atlantic in a large ocean steamer is now as familiar and as little troublesome as the journey from London to Paris. It rarely offers any incident worth recounting, and yet, especially as a first experience, it supplies an abundant variety of sources of curiosity and interest. It is easy
for a man to sit down at home and within the walls of his own study to find the requisite materials for investigating the still unsolved problems presented by the physics and meteorology of the ocean, or the evidence favourable or hostile to the important modern doctrine of the permanence of the great ocean valleys; but in point of fact very few men who stay at home do occupy themselves with these questions, and it is no slight
privilege to feel drawn towards them by the hourly suggestions received during a sea-voyage. Nor is it possible to make light of the simpler pleasures caused by the satisfaction of mere curiosity, when that is linked by association with the pictures on which the fancy has worked from one's earliest childhood onward. The starting of a covey of flying-fish, the fringe of cocos palms rising against the horizon, the Southern Cross and the Magellanic clouds, the reversed apparent motion of the sun from right to left-none of them very marvellous as mere observed facts-are so many keys that unlock the closed-up recesses, the blue chambers of the memory, which the youthful imagination had peopled with shapes of beauty and wonder and mystery.
Some thrill of delightful anticipation was, I presume, felt by many of the passengers who went on board the royal mail steamer Don in Southampton Water on the 17th of March, 1882. Amid the usual waving of handkerchiefs from the friends who remained behind on board the tender, we glided seaward, and by four p.m. were going at half speed abreast of the Isle of Wight. The good ship had suffered severely during the preceding winter on her homeward passage from the West Indies, when the heavy seas which swept her upper deck had carried away the covering of her engine-room, stove in the chief officer's cabin, and severely injured her commander, Captain Woolward. On this occasion our voyage was easy and prosperous, and nothing occurred to test severely the careful seamanship of Captain Gillies, who had taken the temporary command.
On the 19th the barometer, which, in spite of a gentle breeze from south-west, had stood as high as 30-40, fell about a quarter of an inch between sunrise and sunset; and in the night, on the only occasion during the entire voyage, remained for some hours below 30'00. A moderate breeze from the north brought with it a disproportionately heavy sea, and although there was no sensible pitching, the ship rolled so heavily as to send many of the passengers to solitary confinement in their berths. This continued throughout the 20th, afterwards styled Black Monday by the sufferers from sea-sickness, and we escaped into smoother water only on the evening of the following day. The discomfort which I felt from fancying that I had “lost my sea legs "was entirely relieved by fortunately coming across a distinguished naval officer, on his way to take a command on the West Indian station, who like myself was forced to hold on with both hands during the rolling of the ship.
It was clear that we had passed at no great distance from a cyclone in the North Atlantic-one of those disturbances whose visits are so often predicted from the western continent, but which so often fortunately lose their way or get dissipated before they approach our shores. It would seem that little progress has been made in forecasting the direction in which these great aërial eddies traverse the ocean, or the conditions under which they expend their force. It seems allowable to suppose that the most important of the causes influencing their direction depend upon the general movements of the great currents of the atmosphere; and that, as these are
NOTES OF A NATURALIST.
constantly modified by the changing position of the earth in her orbit, the element of season is primarily to be considered. It being admitted that the origin of these disturbances is to be sought in the abnormal heating or cooling of some considerable portion of the earth's surface, it would seem that, in the case of the Atlantic, local causes can have little effect, unless we suppose that the heating of the surface of the Azores in summer, or the annual descent of icebergs from the polar seas, are adequate to influence the march of a travelling cyclone.
On the evening of the 20th the barometer had risen again to its former position, rather over 39 40 inches; the mean of the four following days was 30-55, and that of the entire run from Southampton to Barbadoes was 30*36. This fact of the continuance of high or low pressures at the sea-level at certain seasons in some parts of the world has scarcely been sufficiently noted in connection with the ordinary rules for the measurement of heights by means of the barometer. The tables supplied to travellers are all calculated on the assumption that the pressure at the sea-level is constant—the English tables fixing the amount at 30.00 inches of mercury, those calculated on the continent starting from a pressure of 760 millimetres, or about 29'921 inches. It is admitted that this mode of determining heights, when comparative observations at a known station are not available, is subject to serious unavoidable error. With regard, however, to mountains not remote from the sea-coast, it may be possible to lessen this inconvenience in many parts of the world by substituting