Some Salient Points in the Science of the Earth

by Sir John William Dawson

Tuckerman's Ravine has been formed originally either by a subsidence of a portion of the mountain side, or by the action of the sea. It is, like most of the ravines and "gulfs" of these hills, a deep cut or depression bounded by precipitous sides and terminating at the top in a similarly precipitous manner. It must at one period have been in part filled with boulder clay, steep banks of which still remain in places on its sides; and extensive landslips have occurred, by which portions of the limiting cliffs have been thrown toward the centre of the valley, in large piles of angular blocks of gneiss and mica slate, in the spaces between which grow gnarled birches and spruces that must be used as ladders and bridges whereby to scramble from block to block, by every one who would cross or ascend one of these rivers of stones. These "gulfs" of the White Mountains are similar to the "cirques" of the Alps, and various explanations have been given of their origin. To me they have always appeared to be of the same nature with the "chines" or bays with precipitous ends seen on rocky coasts, and which are produced by the action of the surf on the softer beds or veins of rock. They testify to the raging of the waves for long ages against the sides of what are now lofty mountains. This, we know, must have occurred in the great Pleistocene submergence; but in mountains so old as those now in question, it may have in part been effected in previous periods.

At the head of the ravine we paused to rest, to admire the wild prospect presented by the ravine and its precipitous sides, and to collect the numerous plants that flower on the surrounding slopes and precipices. Here, on the 19th of August, were several large patches of snow, one of them about a hundred yards in length. From the precipice at the head of the ravine poured hundreds of little rills, and several of them collecting into a brook, had excavated in the largest mass of snow a long tunnel or cavern with an arched and groined roof. Under the front of this we took our mid-day meal, with the hot August sun pouring its rays in front of us, and icy water gurgling among the stones at our feet. Around the margin of the snow the vegetation presented precisely the same appearances which are seen in the low country in March and April, when the snow banks have just disappeared—the old grass bleached and whitened, and many perennial plants sending up blanched shoots which had not yet experienced the influence of the sunlight.

The vegetation at the head of this ravine and on the precipices that overhang it, presents a remarkable mixture of lowland and mountain species. The head of the ravine is not so high as the limit of trees already stated, but its steep sides rise abruptly to a plateau of 5,000 feet in height, intervening between Mount Washington and Mount Munro, and on which are the dark ponds or tarns known as the Lakes of the Clouds, forming the sources of the Amonoosook river, which flows in the opposite direction. From this plateau many alpine plants stretch downward into the ravine, while lowland plants, availing themselves of the shelter and moisture of this cul-de-sac, climb boldly upward almost to the higher plateau. Other species again occur here, which are found neither on the exposed alpine summits and ridges, nor in the low country. Conspicuous among the hardy climbers are two coarse and poisonous weeds of the river valleys, that look like intruders into the company of the more dwarfish alpine plants;—the cow parsnip (Heracleum lanatum) and the white hellebore (Veratrum viride). Both of these plants were seen struggling up through the ground at the margin of the snow, and climbing up moist hollows almost to the tops of the precipices. Some specimens of the latter were crowded with the infant caterpillars of a mountain butterfly or moth. Less conspicuous, and better suited to the surrounding vegetation, were the bluets (Oldenlandia cœrulea), now in blossom here, as they had been months before in the low country, the dwarf cornel (Cornus Canadensis) and the twin-flower (Linnæa borealis), the latter reaching quite to the plateau of the lake of the Clouds, and entering into undisputed companionship with the truly alpine plants, though it is also found at Gorham, 4,000 feet lower.

Of the plants which seemed to be confined, or nearly so, to the upper part of the ravine, one of the most interesting was the northern painted cup (Castelleia septentrionalis), a plant which abounds on the coast of Labrador, and extends thence through all Arctic North America to the Rocky Mountains, and is perhaps identical with the C. Sibirica of Northern Asia and the C. pallida of Northern Europe. Large beds of it were covered with their pale yellow blossoms on the precipitous banks overhanging the head of the ravine. With the painted cup, and here alone, was another beautiful species of a very different order, the northern green orchis (Platanthera hyperborea), a plant which occurs, though rarely, in Canada, but is more abundant to the northward. Here also occurred Peck's geum (G. radiatum, var.), Arnica mollis, and several other interesting plants.

Of the alpine plants which descend into the ravine, the most interesting was the Greenland sand-wort (Arenaria (Alsine) Grænlandica) which was blooming abundantly, with its clusters of delicate white flowers, on the very summit of the mountain, and could be found here and there by the side of the brook in the bottom of the ravine.

Clambering by a steep and dangerous path up the right side of the ravine, we reach almost at once the limit, beyond which the ordinary flora of New England can extend no longer, and are in the presence of a new group of plants comparable with those of Labrador and Greenland. Here, on the plateau of the Lake of the Clouds, the traveller who has ascended the giddy precipices overhanging Tuckerman's Ravine is glad to pause, that he may contemplate the features of the new region which he has reached. We have left the snow behind us, except a small patch which lingers on the shady side of Mount Munro; for it is only in the ravines into which it has drifted a hundred feet deep or more, that it can withstand the summer heat until August. We stand on a dreary waste of hard angular blocks of mica slate and gneiss that lie in rude ridges, as if they had been roughly raked up by Titans, who might have been trying to pile Monro upon Washington, but which seem to be merely the remains of the original outcropping edges of the rocks broken up by the frost, but not disturbed or rounded by water.[194] Behind us is the deep trench-like ravine out of which we have climbed; on the left hand a long row of secondary summits stretching out from Mount Washington to the south-westward, and designated by the names of a series of American statesmen. In front this range descends abruptly in great wooded spurs or buttresses to the valley of the Amonoosook, which shines in silvery spots through the trees far below. On our right hand towers the peak of Mount Washington, still more than a thousand feet above us, and covered with angular blocks, as if it were a pile of fragments rather than a solid rock. These stones all around and up to the summit of the mountain, are tinted pale green by the map lichen (Lecidea geographica), which tinges in the same way the alpine summits of European mountains. Between the blocks and on their sheltered sides nestle the alpine flowering plants, of which twenty species or more may be collected on this shoulder of the mountain, and some of which extend themselves to the very summit, where Alsine Grœnlandica and the little tufts of deep green leaves of Diapensia Lapponica with a few Carices seem to luxuriate. Animal life accompanies these plants to the summit, near which I saw a family of the snow bird, evidently summer residents here, instead of seeking the far north for a breeding place, as is the habit of the species, and a number of insects, conspicuous among which was a brown butterfly of the genus Hipparchia. Shortly before sundown, when the thermometer at the summit house was fast settling toward the freezing point, a number of swallows were hawking for flies at a great height above the highest peak. To what species they belonged I could not ascertain. Possibly the cliff swallows find breeding places in the sides of the ravines, and rise over the hill top to bask in the sunbeams, after the mountain has thrown its shadows over their homes.

[194] Hitchcock has since found travelled blocks on the summit, bearing evidence to its submergence under the waves of the glacial sea, and to the grinding of ice floes upon it. Such a fact helps to account for the broken character of the summit, and also implies that unequal subsidence of the land elsewhere referred to, since we know of no agency which could carry boulders so high as the present mountain top.

To return to the Alpine flora which is peculiar to the peaks of these mountains—are the species comprising it autochthones originating on these hill tops, and confined to them, or are they plants occurring elsewhere, and if so, where? and how and when did they migrate to their present abodes? These are questions which must occur to every one interested in geology, botany, or physical geography.

Not one of the Alpine plants of Mount Washington is peculiar to the place. Nearly all of them are distinct from the plants of the neighbouring lowlands, but they occur on other hills of New England and New York, and on the distant coasts of Labrador and Greenland, and some of them are distributed over the Arctic regions of Europe, Asia and America. In short, they are stragglers from that Arctic flora which encompasses the north polar region, and extends in promontories and islands along the high cold mountain summits far to the southward.