Notes of a naturalist in South America

by John Ball

The cold was sufficient to make the little stove in the saloon of the steamer very acceptable, but at no time throughout the voyage could be called severe. Between noon and three p.m. on the 5th of June the thermometer in the open air stood about 40° Fahr., and fell at night only two or three degrees below freezing-point. The barometer was high, gradually rising from 30 inches to 30·3, at which it stood on the following day. Everything promised settled weather, and it was therefore disappointing to find the sky completely covered when I went on deck early in the morning of the 6th. A light breeze from the north raised the temperature by a few degrees and brought the clouds. The scenery throughout the day was even of a grander character than before, and the absence of sunshine gave it a sterner aspect. At times, when passing the smaller islands, I was forcibly reminded of the upper lake of Killarney, the resemblance being much increased by the appearance of the smaller islets and rocks worn down and rounded by floating ice. On this and the following days I frequently looked out for evidences of ice-action on the rocky flanks of the mountains. These were at some points very perceptible up to a considerable height; but all that I could clearly make out appeared to be directed from south to north, and nearly or quite horizontal. I failed to trace any indication on the present surface of the descent in a westerly direction of great glaciers flowing from the interior towards the coast.

Before midday we passed opposite the opening of Eyre Sound, one of the most considerable of the numerous inlets that penetrate the mountains on the side of the mainland. This is said to extend for forty or fifty miles into the heart of the Cordillera, and it seems certain that one, or perhaps several, glaciers descend into the sound, as at all seasons masses of floating ice are drifted into the main channel. We did not see them at first, as the northerly breeze had carried them towards the southern side of the inlet; but before long we found ourselves in the thick of them, and for about a mile steamed slowly amongst floating masses of tolerably uniform dimensions, four or five feet in height out of the water, and from ten to fifteen feet in length. At a little distance they looked somewhat like a herd of animals grazing. Seen near at hand, the ice looked much weathered, and it may be inferred that the parent glacier reaches the sea somewhere near the head of the sound, and they had been exposed for a considerable time before reaching its mouth.

ORIGIN OF THE GLACIERS.

The existence of great glaciers descending to the sea-level on the west coast of South America, one of which lies so far north as the Gulf of Peñas, about 47° south latitude, is a necessary consequence of the rapid depression of the line of perpetual snow on the flanks of the Andes, as we follow the chain southward from Central Chili to the channels of Patagonia. The circumstance that permanent snow is not found lower than about fourteen thousand feet above the sea in latitude 34°, while only 8° farther south the limit is about six thousand feet above the sea-level, has been regarded as evidence of a great difference of climate between the northern and southern hemispheres, and more especially of exceptional conditions of temperature affecting this coast. It appears to me that all the facts are fully explained by the extraordinary increase of precipitation from the atmosphere, in the form of rain or snow, which occurs within the zone where the rapid depression of the snow-line is observed. So far as mean annual temperature of the coast is concerned, the diminution of heat in receding from the equator is less than the normal amount, being not quite 5° Fahr. for 7° of latitude between Valparaiso and Valdivia. But the annual rainfall at Valdivia is eight times, and at Ancud in Chiloe more than nine times, the amount that falls at Santiago. Allowing that the disproportion may be less great between the snowfall on the Cordillera in the respective latitudes of these places, we cannot estimate the increased fall about latitude 40° at less than four times the amount falling in Central Chili. When we further recollect that in the latter region the sky is generally clear in summer, and that the surface is exposed to the direct rays of a sun not far from vertical, while on the southern coast the sun is constantly veiled by heavy clouds, it is obvious that all the conditions are present that must depress the snow-line to an exceptional extent, and allow of those accumulations of snow that give birth to glaciers. When a comparison is drawn between South Chili and Norway, it must not be forgotten that at Bergen, where the Norwegian rainfall is said to be at its maximum, the annual amount is sixty-seven inches, or exactly one-half of that registered in Chiloe.

It is a confirmation of this view of the subject that in going southward from the parallel of 42° to Cape Froward in the Straits of Magellan, through 12° of latitude, while the fall of mean yearly temperature must be reckoned at 8° Fahr., the depression of the snow-line cannot exceed three thousand feet.[33] Of course, we have no direct observations of rainfall in the Channels or on the west side of the Straits of Magellan, but there is no doubt that it diminishes considerably in going southward.

To the south of Eyre Sound the main channel opens to a width of four or five miles, and is little encumbered by rocky islets, so that we kept a direct course a little west of south, and in less than two hours reached the southern extremity of Wellington Island, and gained a view of the open sea through a broad strait which is known as the Gulf of Trinidad. Now that this has been well surveyed, it offers an opportunity for steamers bound southward that have missed the entrance to the Gulf of Peñas to enter from the Pacific, and take the course to the Straits of Magellan through the southern channels.

INTRICACY OF THE CHANNELS.

We had now accomplished the first stage in the voyage through the Channels. Many local names have been given to the various passages open to navigation on this singular coast; but, speaking broadly, the northern portion, between Wellington Island and the mainland, is called Messier’s Channel; the middle part, including a number of distinct openings between various islands, is known as the Sarmiento Channel; and the southern division, between Queen Adelaide Island and the continent, is Smyth’s Channel. Facing the Pacific to the south of Wellington Island are three of large size—Prince Henry Island, Madre de Dios, and Hanover Island, besides countless islets which beset the straits that divide these from each other; and the course followed by the steamers lies between the outer islands and another large one (Chatham Island) which here rose between us and the mainland.

In the afternoon the north wind freshened; as a result, the weather became very thick, and rain set in, which lasted throughout the night. Our intended quarters were in a cove called Tom Bay; but our cautious captain, with a due dislike to “dirty weather,” resolved to halt in a sheltered spot a few miles farther north, known as Henderson’s Inlet. Both these places afford excellent shelter, but the bottom is rocky, and ships are much exposed to lose their anchors. Although we arrived some time before sunset, the evening was so dark, and the general aspect of things so discouraging, that no one suggested an attempt to go ashore. Although we were quite near to land, I could make out very little of the outlines; and, indeed, of this middle portion of the voyage I have retained no distinct pictures in my memory.