Notes of a naturalist in South America

SUN-STROKE.

The most obvious suggestion is that, inasmuch as dry air absorbs less of the solar heat than air charged with aqueous vapour, the injurious effects should be more felt in dry climates than in damp ones. But, so far as what is called sun-stroke is concerned, the balance of evidence is opposed to this conclusion. Sir Joseph Fayrer, who has had wide experience in India, expressly asserts that the hot dry winds in Upper India induce less cases of sun-stroke than the moist though cooler climate of Bengal and Southern India. Dr. Hann quotes Borius for a statement that in Senegambia the rainy season is that in which sun-stroke commonly occurs, while he further asserts that on the Loango coast, in very similar climatal conditions, the affection is almost unknown, and that Europeans even expose the head to the sun with impunity.

My own conclusion, fortified by that of eminent authorities, is that the phenomena here discussed are of a very complex nature; that different physical agencies are concerned in the various effects produced on the body; and that most probably there are many different pathological affections which have been classed together, but which, when more fully studied, will be recognized as distinct.

In the first place, I apprehend that the action of the sun which causes discolouration and blistering of the skin has no relation to that which causes sun-stroke. It is a local effect confined to the surfaces actually exposed, and, if it could be accurately registered, would serve the purpose of an actinometer, depending as it does on the amount of radiant heat reaching the surface in a unit of time.

Sun-stroke proper is, I believe, an affection of the cerebro-spinal system arising from the overheating of those parts of the body. It is by no means confined to the tropics, or to very hot countries, as many cases occur annually in Europe, and still more frequently in the eastern states of North America.

Nearly allied to sun-stroke, but perhaps sufficiently different to deserve separate classification, are those attacks which some writers style cases of thermic fever, which arise mainly in places where the body is for a continuance exposed to temperatures exceeding the normal amount of the human body. In producing thermic fever, it would appear that the depressing effect of a hot moist climate acts powerfully as a predisposing cause, and such cases not uncommonly arise where there has been no exposure whatever to the direct rays of the sun.

PERNAMBUCO.

It is easy to understand that, as a general rule, seamen are less exposed than other classes to any of the injurious effects of heat, but it is remarkable that they should enjoy complete exemption. Cases are not very uncommon among seamen going ashore in hot countries, but I have not found a well-authenticated case of sun-stroke arising on board ship; and cases of thermic fever in the Red Sea usually arise in the engine-room of a steamer rather than among the men on deck.

On the morning of July 29 we reached Pernambuco, to which I had looked forward as the last Brazilian city that I was likely to see. It had been described to me as the Venice of South America, and the comparison is to a slight extent justified by its position on a lagoon of smooth water, separated from the open roadstead by a coral reef several miles in length. It enjoys the further distinction, unusual in a place within eight degrees of the equator, of being remarkably healthy. But on this occasion fortune was against me.

No doubt for some sufficient reason, we did not enter the rather intricate passage leading inside the reef, but lay to in rough water outside. For a short time the scene was brilliant. The hot sun beat down on the deep blue water, and lit up the foam on the crests of the dancing waves, and the sky overhead showed such a pure azure that one could not suppose the air to be saturated with vapour. Before long boats were seen approaching, tossed to and fro in the broken water; but before they drew near, heavy clouds had gathered in the course of a few minutes, and a torrent of water was discharged such as I had never experienced except in passing under a waterfall. As each boat came alongside, a seat was let down from the upper deck, and the passengers were hoisted up in turn, those who had not efficient waterproofs being as thoroughly drenched as if they had been dipped in the sea. Four or five times during the day the sky cleared, the blazing sun returned, and the decks were nearly dry, when another downpour of torrential rain drove us all to seek shelter, each shower lasting only from ten to fifteen minutes.

During the hotter hours of the day a rather strong breeze set in towards the shore, and I have no doubt that it is to its full exposure to this ordinary sea-breeze that the city owes its comparative healthiness. It was interesting to watch the manœuvres of the catamarans, in which the native fishermen were pursuing their avocations. This most primitive of sea-craft is formed of two or three logs well spliced together, with some weight to serve as ballast fastened underneath. In the forepart a stout stick some ten feet long stands up as a mast and supports a small sail, and amid-ships a short rail, supported on two uprights, enabled the two men who form the crew to hold on when much knocked about by the waves. A single paddle seems to serve as a rudder, but it is not easy to understand how such a rude substitute for a boat is able to work out to sea against the breeze which commonly sets towards the shore.

A large proportion of the steerage passengers who came on board at Bahia and Pernambuco were Portuguese returning to their native country after a residence, either as artisans or as agricultural settlers, in Brazil. My command of the language is unfortunately so limited that I failed to extract from these fellow-passengers any interesting information. With scarcely an exception, each carried at least one parrot, usually intended for sale at Lisbon, where it appears that they are in some request. Comparatively high prices are given for birds that freely simulate human speech.

THE ANEROID BAROMETER.

We were under steam in the afternoon of the 29th, and soon lost to view the South American continent. On the following day the barometer for the first time showed the diminution of pressure which is normally found in the equatorial zone. Between nine a.m. and four p.m. the ship’s mercurial barometer fell about a quarter of an inch from 30·30 to 30·06 inches, and my aneroid showed nearly the same amount of difference. It must be remembered, however, that nearly one-half of the effect (at least one-tenth of an inch) must be set down to the daily oscillation of the height of the barometer, which so constantly occurs within the tropics, the highest pressures recurring at ten a.m. and ten p.m., and the lowest about four p.m. and four a.m.

I carried with me on this journey only a single aneroid barometer, an excellent instrument by Casella, whose performance was very satisfactory, and which in a very short time returned to its normal indication after exposure to diminished pressure in the Andes; but it had the defect, which, so far as I know, is common to the aneroid instruments by the best makers, that the temperature at which the scale is originally laid down by comparison with a standard mercurial barometer is not indicated on the face of the instrument. Assuming that the aneroid is compensated for variations of temperature, and I have found this to be the case within ordinary limits in good instruments, there remains the question to what height of mercury at what temperature a given reading of the aneroid corresponds. For scientific purposes it is customary to reduce the reading of the mercurial barometer to the temperature of the freezing-point of water, and it is often supposed that the aneroid reading corresponds to that figure. But we may feel pretty confident that the maker, in laying down the scale, did not work in a room at freezing-point. I have been accustomed to assume 15 °Cent., or 59° Fahr., as about the probable temperature with instruments made in our climate.

In the present case, the barometer-reading of 30·06 inches at the temperature of 84° Fahr. would (neglecting the small correction for capillarity) be reduced by about fourteen-hundredths of an inch, in order to give the correct figure at freezing-point; but for comparison with an aneroid, supposed to have been laid down at 59° Fahr., the correction would be a fraction over seven-hundredths of an inch. As a matter of fact, my aneroid marked at four p.m. 29·89 inches, or, allowing for the correction, just one-tenth of an inch less than the ship’s mercurial barometer, and, as I believe, was more nearly correct.

As the sun was declining on the evening of July 30, we sighted the remarkable island of Fernando Noronha. It lies about four degrees south of the equator, and more than two hundred miles from the nearest point of the Brazilian coast. The outline is singular, for the rough hills which cover most of the surface terminate at the western end of the island in a peak surmounted by a column, in the form of a gigantic lighthouse, which must rise over a thousand feet above the sea-level.47 Although Darwin passed some hours on the island in 1832, it remains to the present day one of the least known of the Atlantic islands, so far as regards its natural productions. A fellow-passenger who had landed there assured me that he had found granite; but I have no doubt that the island is exclusively of volcanic origin, for such is the opinion of the few scientific men who have visited it.

FERNANDO NORONHA.

The island has been converted by the Brazilian Government into a convict station, and in consequence access by strangers has become very difficult. Such information as we possess is mainly to be found in Professor Moseley’s account of the voyage of the Challenger. On landing there with Sir G. Nares, he at first obtained permission from the governor to visit the island and to collect natural objects; but the permission was very soon retracted, and he was unable to obtain specimens of several singular shrubs that abound and give the island the appearance of being covered with forest.

Now that the attention of naturalists has been directed to the especial interest attaching to the fauna and flora of oceanic islands, and their liability to extinction owing to competition from species introduced by settlers, it may be hoped that the exploration of this small but remarkable island will before long be undertaken by a competent naturalist. For that purpose it would be, in the first place, necessary to obtain the permission of the Brazilian Government, and to secure the means of existence during a stay of ten or twelve days on the island. The most effectual means would be through direct personal application to the emperor, who is well known to take a lively interest in all branches of natural science.

With the thermometer standing about 82°, the passengers naturally preferred the upper deck to the close air of the saloon, and were resting in their ship-chairs between nine and ten p.m., when suddenly there came an outburst of coughing and sneezing, followed by demands for muffling of every kind. There was no sensible movement in the air, but I found that the thermometer had fallen to 79° Fahr., and there was a feeling of chilliness which was not easily explained by that slight fall of temperature.

The mystery was explained on consulting the chief officer, who throughout the voyage paid much attention to the temperature of the sea. Since leaving Pernambuco, the thermometer in buckets brought up from the surface had varied only between 82° and 83°. On this evening we had abruptly encountered a relatively cold current, with a temperature somewhat below 76°, and the effect of being surrounded by a body of cool water when the skin was in the condition usual in the tropics was felt by nearly all the passengers.

M. GEORGES CLARAZ.

With slight variation, this comparatively cool current must have extended over a large area on both sides of the equator, as the temperature of the water remained nearly the same for about forty-eight hours.

Throughout the voyage from Brazil to Europe, I was fortunate in enjoying the society of a man of remarkable intelligence, who has been a diligent and accurate observer of nature in a region still imperfectly known. M. Georges Claraz, by birth a Swiss, belonging to a family of small proprietors in the Canton of Fribourg, had gone out as a young man to improve his fortune in South America. He had received a fair scientific education, having followed the lectures of the eminent men who have adorned the Polytechnic School at Zurich; but, what is much more rare, he appeared to have retained everything that he had ever learned, and to have had a clear perception of the scientific value of the observations that a stranger may make in a little-known region. After passing some time in the state of Entrerios, he had settled at Bahia Blanca, close to the northern border of Patagonia. He had established friendly relations with the Indians, and made frequent excursions in the interior of Patagonia and southward as far as, and even beyond, the river Chubat.

During the entire time, although engaged in the work of a settler, M. Claraz seems to have made careful notes of his observations – on the native Indians and their customs; on the indigenous and the domestic animals; on the plants and their uses; on the mineral structure of the country, not omitting to take specimens of the mud brought down by the different rivers; and on general physics. Of his large collections I trust that the greater part have safely reached Switzerland. A considerable collection of dried plants, sent home while he resided at Bahia Blanca, was unfortunately lost. He was good enough, after his return, to send me a smaller collection remaining in his hands, of which I gave an account in the Journal of the Linnæan Society for 1884.

As I trust that the great store of information collected by M. Claraz will before long be given to the world, I should not wish to anticipate the appearance of his work, but I may say that among many interesting particulars, several of which I noted at the time, I was especially struck by the evidence collected among the Indians, which seemed to prove that the Glyptodon survived in Patagonia down to a comparatively recent period, and that the tradition of its presence is preserved in the stories and songs of the natives.

Early on July 31 we passed the equator, but it was not till ten p.m. on the following day that we escaped from the area of cool water and found the ordinary equatorial temperature of 82·5°. During the three following days the weather was hot and relaxing, the thermometer ranging by day between 84° and 85°. For some hours on the 2nd of August the wind came from south-south-east, but before evening it backed to west, and blew from that point rather freshly at night. On the following day we appeared to have met the north-east trade-wind, which was, however, a gentle breeze, and occasionally veered to the north-west.

ISLAND OF ST. VINCENT.

In the afternoon of August 4 we made out the picturesque outline of the Cape Verde Islands, and before sunset entered the channel between St. Vincent and St. Antão, finally dropping anchor for the night in the outer part of the fine harbour of St. Vincent. Having been selected as a coaling station, this has become the chief resort of steamers plying between Europe and the Southern Atlantic, and we were led to expect that the operation would take up great part of the following day. Here a fresh disappointment awaited me. I had confidently reckoned upon spending several hours ashore, and seeing something of the curious vegetation of the island, which includes a scanty representation of tropical African types, with several forms allied to the characteristic plants of the Canary Islands.

I had not duly taken account of the perverse temper of the officers of health, whose chief object in life seems everywhere to be to make their authority felt by the needless annoyance they cause to unoffending fellow-creatures. We had left Rio with a clean bill of health; not a single case of yellow fever had occurred for months before our departure; but Brazil is regarded as permanently “suspected,” and quarantine regulations were strictly enforced in our case.

I am far from believing that in certain conditions, and as regards certain diseases, judicious quarantine regulations may not be effective; but, reckoning up all the loss and inconvenience, and the positive damage to health, arising from the sanitary regulations now enforced, I question whether it would not be better for the world if the system were entirely abolished.

The view of St. Vincent, backed by a bold and stern mountain mass, on which scarcely a trace of vegetation is visible from a distance, was for some time sufficiently interesting; but as the day wore on, and the sun beat down more fiercely, life on board became less agreeable. To keep out the penetrating coal dust all the ports were closed, and, with the thermometer at 90°, the air below was stifling, and the passengers generally preferred to remain on deck, and breathe the hot air mixed with the coal dust that arose from the open bunkers.

I offered two of the boatmen who hung about the ship three milreis if they would land on an uninhabited part of the bay, which I pointed out to them, and collect for me every plant they found growing, and I was well pleased when, after two or three hours, they returned with a respectable bundle of green foliage. Under the vigilant eyes of the officers of health the specimens were hauled up to the deck, while the three dollars were thrown into the boat. It is remarkable that coin is nowhere supposed to convey contagion.

When I came to examine it, I found to my disgust that the bouquet included only the leaves of two species, with no trace of flower or fruit. One was most probably Nicotiana glauca, introduced from tropical America; the other a leguminous shrub, possibly a Cassia, but quite uncertain.

The rest of the passengers spent most of the day in bargaining with the hucksters who flocked round the ship. Ornaments made from palm leaves, sweetmeats of very suspicious appearance, photographs, and tobacco in various forms, were the chief articles of traffic, and the main object seemed to be to prolong the chaffering and bargaining over each article so as to kill as much time as possible. More attractive in appearance were the tropical fruits, of which those suitable to a dry climate grow here in perfection. In spite of persevering efforts, I have never developed much appreciation of the banana as an article of diet, but I thought those obtained here much the best that I have anywhere eaten.

ATLANTIC TRADE WINDS.

General satisfaction was felt when, the work of coaling being finished, the ship was again in motion, with her head set towards Europe. On returning to the channel between the islands, and still more when we had got well out to sea, we encountered a rather strong breeze right ahead, which with varying force continued for the next four days. This was, of course, the regular trade-wind of the North Atlantic, and had the agreeable effect of lowering the temperature, which at once fell to 78°. Along with the trade-wind, the sea-current apparently travels in the same direction. It is certain that the temperature of the water was here much lower. Before reaching St. Vincent we found it between 80° and 81° Fahr., while after leaving the islands it had fallen to 74°. This temperature remained nearly constant for three days, but on the evening of the 9th, in about 27° north latitude, we abruptly encountered another current of still cooler water, in which the thermometer fell to 69°.

The force of the wind never, I think, exceeded what seamen describe as a fresh breeze, but it sufficed to cause at times considerable disturbance of the surface; and on the afternoon of the 6th we shipped some heavy seas, so that it was found expedient to slacken speed for a time.

I have alluded in a former page to the ordinary observation that in the track of the trade-winds the breeze usually falls off about sunset. It is more difficult to account for the opposite phenomenon, which we experienced on three successive evenings from the 7th to the 9th of August, when the force of the wind increased in a marked degree after nightfall.

I was also struck by the fact that the temperature of the air throughout the voyage from St. Vincent to the mouth of the Tagus seemed to be unaffected either by the varying force of the wind or by the fall in surface-temperature of the sea, to which I have above referred. On board ship in clear weather it is very difficult to ascertain the true shade temperature when the sun is much above the horizon, but the observations made at sunrise and after nightfall from the evening of the 5th to the morning of the 11th varied very slightly, the utmost range being from 77·5° to 73°.

Some points in the Canary Islands are often visible in the voyage from Brazil to Europe, especially the lofty peak of Palma; but we passed this part of the course at night, and nothing was seen. As we drew near to Europe, the wind, through keeping the same direction, gradually fell off to a gentle breeze, and the surface of the water became glassy smooth, heaving gently in long undulations. The relative effect of smooth or rough water on the speed of steamers is remarkable, and was shown by the fact that during the twenty-four hours ending at noon on the 11th of August the Tagus accomplished a run of 295 knots, while three days before, with only a gentle breeze but rougher water, the run to noon was only 240 knots.

THE TOWER OF BELEM.

Early in the afternoon of the 11th, the Rock of Lisbon at the mouth of the Tagus was distinctly visible, and we slowly entered the river and cast anchor at the quarantine station below Belem. Our captain, after the experience of St. Vincent, did not expect to obtain pratique at Lisbon, and with more or less grumbling the passengers had made up their minds to remain on board, when, after a long deliberation, the unexpected news, “admitted to pratique,” was rapidly spread through the ship, and we moved up to the anchorage opposite the picturesque old tower of Belem, which the true mariner must always regard as one of his holy places. It marks the spot wherefrom Vasco de Gama and his companions, after a night spent in prayer in the adjoining chapel, embarked on their memorable voyage, and here, after years of anxious uncertainty, King Manuel greeted the survivors on their return to their country.

The sun was sinking when such passengers as wished to see something of Lisbon took the opportunity for going ashore, while others, like myself, preferred to remain on board. Hoping to receive letters at the post-office, I landed early next morning, and found a tramcar to carry me to the centre of the town. Early hours are not in much honour at Lisbon. I found the post-office closed, and, after several vain efforts, was informed that letters could not be delivered until ten o’clock, the precise hour fixed for our departure from the anchorage at Belem.

The voyage from Lisbon along the coasts of Portugal and Galicia is usually enjoyed, even by fair-weather sailors. The case is often otherwise with the Bay of Biscay, but on this occasion there was nothing of which the most fastidious could complain. I have sometimes doubted whether injustice has not been done to that much-abused bay, which, in truth, is not rightly so called by those bound from the north to the coast of Portugal. It is simply a part of the Atlantic Ocean, adjoining the coast of Europe between latitudes 43° 46′ and 48° 28′. I have not been able to ascertain that the wind blows harder, or that the sea runs higher there than elsewhere in the same latitudes, and am inclined to rank the prejudice against that particular tract of sea-water among vulgar errors.

The adventurer who has attempted to open up a trade with some distant region is accustomed, as he returns home, to count up the profits of his expedition; and in somewhat the same spirit the man who pursues natural knowledge can scarcely fail to take stock of the results of a journey. It is his happy privilege to reckon up none but gains, and those of a kind that bring abiding satisfaction. He may feel some regret that outer circumstance or his own shortcoming have allowed opportunities to escape, and lessened the store that he has been able to accumulate; but as for the positive drawbacks, which seemed but trivial at the time, they absolutely disappear in the recollection of his experiences. Thinking of these things as the journey drew to a close, I could not help feeling how great are the rewards that a traveller reaps, even irrespective of anything he may learn, or of the suggestions to thought that a voyage of this kind cannot fail to bear with it. How much is life made fuller and richer by the stock of images laid up in the marvellous storehouse of the brain, to be summoned, one knows not when or how, by some hidden train of association – shifting scenes that serve to beautify many a common and prosaic moment of life!