Popular Science Monthly/Volume 66/March 1905/The Bermuda Islands and the Bermuda Biological Station for Research I
|THE BERMUDA ISLANDS AND THE BERMUDA BIOLOGICAL STATION FOR RESEARCH.|
By Professor EDWARD L. MARK,
DIRECTOR OF THE ZOOLOGICAL LABORATORY, HARVARD UNIVERSITY.
I FEEL a certain hesitancy in speaking on the subject I have selected to talk about—the Bermuda Islands—because of the number of prominent naturalists who have written so excellently about them. It should be stated at the outset that I do not aim to add to the stock of our knowledge about the Bermudas. So much has been written about their zoology in recent years—especially by the zoologists of the Challenger Expedition, then by Professor Heilprin of this city, on the invertebrates and the coral reefs, by Mr. Agassiz, incidental to his studies of the great question of the origin and growth of coral reefs, and most recently by that veteran in systematic zoology, Professor Verrill, of Yale University—that it is hardly to be expected that anything fundamentally new will be soon added. It is my purpose, rather, to give something of a picture of the present conditions in Bermuda, based partly on my own experiences, and particularly to direct your attention to the accessibility of the islands and their availability as a place for carrying on intensive rather than extensive researches. With the facilities for work which will soon be provided by the colonial government, it should be an attractive place not only for temporary exploration and summer study, but also for protracted investigations on important biological problems.
My own interest in Bermuda as a place for zoological study was first awakened by suggestions of President Eliot, who a few years ago passed the winter in Bermuda, and upon his return inquired of me if I did not think it would be a good place for a marine laboratory. The more I inquired into the condition of living in the islands, and the marine organisms in the sea about the islands, the more I became convinced of the practicability of the place for a biological laboratory.
At the risk of saying much that is already familiar to many of you, I will give an account of some of the things which seem to me of interest in this connection.
From fifty to sixty hours' steaming brings one from New York to Bermuda. It is worthy of note that the distance of the islands from New York or Boston is only about two thirds that of the Dry Tortugas or the Bahamas. The climate and the conditions of life in the Bermudas are safe and agreeable at all seasons of the year. Though the humidity is considerable, the temperature in summer rises to only 85° or 86° Fahrenheit; in winter it seldom gets below about 50°, and never to the freezing point. To the zoologist familiar with the animals of our north Atlantic coast and the water they live in, the waters that wash the shores of these islands and the brilliantly colored animals that inhabit them are a source of surprise and delight.
Leaving New York a little before noon on Saturday, the islands are usually sighted about mid-day on Monday, and landing is made in Hamilton a few hours later. If one has pictured to himself low-lying coral islands fringed with palm trees, he will be disappointed, and will be surprised to find that the land rises in many places to a considerable height—even to two hundred and fifty feet or more—and on approaching nearer to see, instead of palms, the dark green of the cedars that cover many of the hills. In passing from the deep waters of the Atlantic to the shallower depths near land, the dark blue of the ocean is replaced by livelier tints, in which greens predominate, and when the conditions of sun and sky are favorable, the variety of colors exhibited is truly wonderful. Even the far-famed Bay of Naples does not afford a more brilliant display of colors than is sometimes seen in the waters around the Bermudas.In contrast with these fascinating, kaleidoscopic effects of the sea, the land presents either the dull gray appearance so common on the granite shores of New England, or the dark green of the cedars, which also reproduce the effect of the New England evergreens. If one could ignore the colors of the sea, he might easily imagine, as he steams along the northern shores of the Bermudas, that he was skirting some part of the Maine coast. One thing, however, would impress him as strange—the brilliant white specks and patches which here and there dot the hillsides or are clustered into larger or smaller groups—the limestone dwellings of the Bermudians. These with their white roofs, brilliant in the sunlight, are in marked contrast to anything seen on
Map 1. Chart of the Bermuda Islands, with Soundings in Fathoms, the Hundred, fathom Line (Dotted), the Ship Channel (Dashes), and the Latitude and Longitude to M nu ES.
Map 2. Northeastern Third of the Bermuda Islands, with Latitude and Longitude Lines Ten Seconds Apart.
the Maine coast. Government House, on Mount Langton—the residence of the governor of the islands—is a conspicuous building on the crest of the ridge which hides the city of Hamilton from the approaching voyager.
After a long and rather circuitous course through the only channel available for steamers, and under the guns of several forts, one at length enters Hamilton Harbor between two rocks that are not far enough apart to allow the passage of two ships abreast. The still unfinished cathedral, two modern hotels for the accommodation of winter tourists, and the parliament house are the most conspicuous buildings in Hamilton, being situated on the highest part of the slope occupied by the town (Fig. 1).
The substantial city dock, with its low, unattractive sheds roofed in by arched and corrugated metal, extends along the whole water front.
Beyond the sheds runs Front Street (Fig. 2) parallel to the shore. Across the street from the sheds are the chief business houses of the town; some of them having a modern look, but the greater part of them with small windows and heavy solid wooden shutters that recall the northern country store of fifty or seventy-five years ago. Unlike the country store, however, the Bermuda store has a two-story portico extending out over the side-walk, so that the pedestrian is partly sheltered by it from the heat of the sun or the sudden down-pour of the unannounced shower that is so characteristic of the islands. The second story of this portico, like most of the dwellings (compare Fig. 3), is enclosed by shutters with immovable slats, which keep out heat and rain, but permit a free circulation of air within. The vehicles in the street range from the modern rubber-tired victoria to the low two wheel cart drawn by horse, mule or ox.
As a glance at the map will show (Map 1), the Bermudas consist of a chain of about half a dozen islands so grouped that the whole bears a fancied resemblance to a gauntlet. The broad wrist region at the northeast is made up of St. David's, Smith's and St. George's islands and a part of the main, or Bermuda, island, the rest of which stands for the hand, the thumb and the first joints of the fingers, the remaining joints of the fingers being represented by Somerset and Ireland islands. The whole length of the group from northeast to southwest is about fifteen miles, and the width is usually a mile or at most two miles; in many places it is much less. A fairly continuous ridge occupies the axis of the islands mentioned. Besides these larger islands, there are numerous smaller ones (Fig. 4), so that it may well be that there is, as claimed, an island for every day in the year. The larger islands are so indented by bays and sounds that it is evident they will
Map 4. Southwestern Third of the Bermuda Islands.
though there are several underground connections. This single surface connection is by means of a passage only about thirty feet wide, through which the water rushes with great swiftness during every tide. It is surprising for how short a time at the turn of the tide, five or ten minutes only, the water is relatively quiet. This narrow passage leads directly to the Flatts Inlet, which in turn connects with the great north lagoon. The inlet, not being very broad, is therefore swept by a rather strong current. This region ('The Flatts,' Map 1) is of particular interest to us, for it is on this inlet that our laboratory is located.
All the waters held, as it were, in the hand of the fancied gauntlet—Great Sound, Little Sound (Map 4), Hamilton Harbor (Map 3),
etc.—form another extensive landlocked sea. which formerly, in all probability, communicated less freely with the north lagoon than at present, for a submarine ridge runs out from Spanish Point—the tip of the thumb (Map 1)—to Ireland Island. At several points this ridge is awash at low tide.
Through the greater part of the main island there are three parallel roads (Map 3): one—known as the middle road—runs in a general way along the ridge; the others—known as north and south roads—run along the north and south shores. The north and middle roads meet at The Flatts, and nearly all the travel between the only two cities, Hamilton and St. George's, passes over the bridge which crosses the gorge between the inlet and Harrington Sound.
The houses of Bermuda are, almost without exception, made of the limestone rock which everywhere abounds. This is cut into blocks a foot or more in length, eight or ten inches wide and of different thicknesses.
Even the roof is made of thin overlapping slabs of the same rock supported by slats that rest on wooden rafters. The houses, roof
and wall, are whitewashed at frequent intervals, usually twice a year. The rain that falls on the roofs is carefully collected in covered cisterns, for it is the only source of fresh water in the islands, since there are no streams, and most of the rain pools last but a few hours even after the heaviest shower. In some localities barren tracts of land are denuded, the rock cut to a sloping surface and whitewashed to serve as a watershed for collecting rain water in larger quantity than the roofs supply.
In addition to the garrisons and the marines there are on the islands about 18,000 people, two thirds of whom are negroes, the rest whites, mostly of English extraction. There is a property qualification for voting; the proportion of whites to blacks on the voting list is two to one, the reverse of the ratio in population.
The cities, as I have said, are but two: the quaint town of St. George's and the more modern town of Hamilton. St. George's is the more interesting because of its tortuous narrow streets, its high garden walls and its ancient architecture, which suggest a medieval European town (Fig. 6). It was the seat of government until about a hundred years ago (1815) and retained for a long time after that an importance due largely to its fine harbor.
The visible land of Bermuda gives a very incomplete idea of the shape of the submarine plateau from which it rises. If the sea were to recede so that its surface was about thirty feet below its present level, we should have a great oval lagoon some twenty-five miles long and from twelve to fifteen wide, the rim of which would be made up in part of the present land area, and for the rest of a more or less continuous reef of coral-covered rocks a mile or so wide (Map 1). The great central basin—the great north lagoon, as I have called it—would have no considerable depth—seldom more than fifteen or twenty feet of water, and nowhere more than thirty—and would be studded with innumerable coral rocks and islands. Some of the deeper parts have special names, as Murray Anchorage and Grassy Bay, while the shallower parts are known as flats—Brackish Pond Flats, Bailey's Bay Flats, etc. The passages through this rim would be only three: Hogfish Cut, Chub Cut and the Narrows or Ship Channel. The slope of the sea bottom outside the rim is rather abrupt on the southeast side of the oval, less so on the northwest side, and least of all at the ends, as the position of the hundred fathom line shows. Beyond the hundred fathom line the bottom slopes even more rapidly to a depth of 1,200, 1,500 or even in places to 2,000 fathoms. These depths are reached at from two to five miles beyond the hundred fathom line.
Rising from the floor of the sea some ten or twelve miles to the southwest of this oval plateau is another much smaller one, which would still be some 150 or 200 feet under the surface were the sea to recede, as we have imagined, thirty feet. This is known as the Challenger Bank.
Ten miles beyond this is another similar plateau of about the same size and height, called the Argus Bank. These two banks are in reality a part—two detached peaks, as it were—of the great submarine mountain of which the Bermuda Islands are the visible summit. For
while the floor of the ocean sinks within five miles to about 1,500 fathoms, these plateaus are separated from each other and from the Bermuda plateau by less than half that depth.
The present land area of all the Bermuda Islands is composed of calcareous rock which varies from a loose sand to a firm, hard, semi-crystalline limestone that resounds to the blow of the hammer. What underlies this, no one yet knows. The deepest excavations—those for the new Navy Yard docks at Ireland Island—have not disclosed any other kind of rock. The numerous deep cuts for roads (Fig. 7) and the quarries which are met with in all parts of the islands tell the same story. The rocks are composed of wind-blown calcareous sand. This sand, contrary to what was formerly supposed, is not composed of broken down corals. These are present only in small proportion, the chief constituents being fragments of shells, serpula tubes and corallines. There are no such stratified subaqueous rocks as are found in this country, but everywhere the cut edges of the rocks show the peculiar sinuous lines that characterize the stratification of drifting sands. Most—if not all—of the harder rocks are doubtless the result of the action of water and air on these aeolian masses. At almost every point where the action of the sea is traceable it has resulted either in cementing together the layers of these rocks till all evidence of stratification is
lost, or else its mechanical effect has been more immediate than its chemical, and the rock has crumbled into its constituent grains and has become once more a sandy beach, in turn yielding up its substance to build the present sand dunes of the coast, which have the same æolian structure as their predecessors.The mechanical action of the sea operating on the already hardened rocks has left them carved in the most fantastic shape (Figs. 8, 9), and with edges so sharp that it is almost impossible to walk upon them. In many places the rocks are honeycombed through the action of water, and subterranean passages connect inland waters with the sea. Caves, too, sometimes of considerable extent, are found at various places, especially
Fig. 9. Cathedral Rocks, looking North. Photograph by A. H. Verrill.
in the northern part of the islands, about Castle Harbor and Harrington Sound. The floors of these eaves are in some places below sea level, and since there is a free communication with the sea, deep pools of sea water are not uncommon in them. The water is so clear and unruffled that the incautious visitor is liable to walk into the pools unawares, even after being especially cautioned against it. The stalactite and stalagmite formations point to the solvent action of water as the cause of the caves. It is highly probable that many of the depressed areas of the land known as 'sinks,' as well as the sounds and harbors, are the result of the falling in of the roofs of caves. The 'sinks' vary in area from a few square yards to many acres.
These depressions contain the peculiar reddish brown earth that makes farming and gardening possible in the Bermudas. The richness of this soil and the favorable climate allow the farmer to keep the earth under constant cultivation and to procure several crops in the course of a year.
Although trees and shrubs in great variety are to be found in Bermuda, most of them are not peculiar to the islands, but probably owe their origin to introduction by natural agencies from the West Indies and the United States before historic times, while many are known to have been introduced by man, and not a few of these within comparatively recent times. The Bermuda cedar (Juniperus bermudiana) may be indigenous, though fifty years ago it was also found in the Blue Mountains of Jamaica. The palms—a dozen species of which are said to be growing in the islands—and the palmettos, are the most noticeable growths to attract the eye of the northener. The royal palm (Fig. 10) surpasses all others both in height and in beauty, but the cocoanut palm (Fig. 11) is a worthy second, and many specimens of it are striking features of the landscape. In Queen Street, Hamilton, one drives beneath the sprawling branches of what we call a 'rubber plant' when it grows in pots in our conservatories. Here its branches have a spread of a hundred feet or so. On entering the Public Garden at St. George's, where many interesting exotics are found, one is confronted by a stately screw pine of most symmetrical form twenty or thirty feet high, and in the Agricultural Gardens near Hamilton, another Pandanus of less graceful form but greater breadth is seen. Our common deciduous trees, however,—the maples, beeches, birches and oaks—are entirely wanting. In a private garden that contained many interesting trees and shrubs from various parts of the world
I was shown, as one of the greatest of curiosities, a sickly specimen of one of our oaks. Even with the utmost care and attention these trees can not be made to flourish in Bermuda; but oleanders have been introduced and flourish almost beyond belief. They are often used as hedgerows and grow to a height of twenty or twenty-five feet. A great variety of tints from deep scarlet—almost crimson—to pure white are to be seen. From May to September they enliven the face of the land with their brilliant colors, which occur in such masses that they are the admiration of all who see them. On the bleak north shores, the tamarisk has been planted as a break against wind and salt-water. Though not an especially graceful shrub, the soft green of its fine-cut foliage makes a pleasant impression on the eye, and it enjoys the great practical advantage of being about the only kind of verdure that can really thrive in the presence of the abundant salt-spray which the prevailing winds drive in upon the land.
The fiddle-wood tree (Citharexylum quadrangulare) is to-day the commonest of the deciduous trees in Bermuda, but the first tree of this species on the islands—the one from which all the others are reported to have come—was imported as recently as 1830, and is still standing. The Pride of India (Melia azedarach) is a rather scraggy, forlorn looking tree in mid-summer, and one wonders why it is so much cultivated; but in early spring, before the leaves are out, it puts forth a profusion of pink flowers that makes it a great favorite with the Bermudians. It seems as though Bermuda must be the home of the genius Hibiscus, so many species are met with. In mid-summer their blossoms exhibit some remarkably gorgeous colors. Still, the most superb of all the ornamental trees and shrubs to be seen here is the Poinciana regia, a native of Madagascar, a tree with spreading branches clothed in the most pleasing green and decked with beautiful clusters of brilliant red blossoms.
The land animals, with the exception of insects and mollusks, are remarkably few, and of these most are probably not natives of the islands any more than are the majority of the phænogamic plants.
Except for domesticated animals, mammals are numerous neither in species nor in individuals. The most interesting one is doubtless the wood rat (Mus tectorum), which lives in trees and is now nearly extinct. This was at one time a dreaded scourge to the early settlers. Nearly 300 years ago (1619), Governor Butler, writing of the timely arrival of a so-called runaway frigate that brought food and thus averted impending famine, said:
It is by no means certain, however, that these rats had not long existed on the islands, even though an earlier writer—Silvanus Jourdan, says (1610):
Whales, which were once of some commercial importance to the islands, are so rare that they are no longer hunted, and the 'whale houses,' of which there were recently half a dozen in existence, are but relics of an industry that has practically ceased.
The greater part of the 150 or more birds mentioned by Major Wedderburn (Jones: 'The Naturalist in Bermuda') as found in the Bermudas, are migrants. The most conspicuous and interesting
of them is the tropic or boatswain bird (Fig. 12), which still continues to nest here, usually on the more remote and inaccessible islands. The only representative of the Amphibia is the great Surinam toad (Bufo agua), which was introduced into Bermuda some twenty-five or thirty years ago by Captain Nathaniel Vesey to combat insect pests. I was fortunate enough during my first visit to the islands to find several of these toads spawning on the morning of April 22. There had been a heavy shower during the preceding night, which had resulted in temporary pools of fresh water in a few places, and it was in one of these pools near Spittal Pond that a half dozen or more pairs were found. A quantity of the spawn was secured and a series of eggs preserved.
Reptiles have at present very few representatives. There are no snakes, and the possible importation of them is carefully guarded against. The only land reptile is the Bermuda lizard (Eumices longirostris), which is not found elsewhere and is probably indigenous. Of turtles, four species, none of which is peculiar to Bermuda, are known to frequent the islands:—the green turtle (Chelonia mydas), the hawk bill (Erctmochelys imbricata), the logger-head (Thalassochelys caouana) and the trunk or leather turtle (Sphargis coriacea). The green turtle is still caught in nets in small numbers, but the others are found only occasionally. From the accounts of several of the early writers on Bermuda it is evident that some of the turtles (perhaps the green turtle) were once very abundant. Sylvanus Jourdan, writing of the shipwreck of Sir George Somers in 1609, says:
An early account of their egg-laying, by Peter Martyr, is given in these words:
It is, however, the richness of the life in the sea—in marked contrast to the paucity of that on land—which is the chief source of attraction to the zoologist. If the gardens on the land require much attention and are the reflection of man's assiduity in transplanting the products of one country to the soil of another, the gardens of the sea demand no such care, and man has had little or nothing to do with shaping the wonderful display of marine life that carpets the floors of the broad lagoons and the reefs of the Bermuda plateau.
(To be concluded.)
- A vice-presidential address prepared for Section F (Zoology) of the American Association for the Advancement of Science, at its Philadelphia meeting.
- I am greatly indebted to Professor A. E. Verrill for the use of about half of the figures, those which he has furnished having been taken from The Transactions of the Connecticut Academy of Science and from his 'The Bermuda Islands,' New Haven, 1902, and 'Zoology of the Bermudas,' New Haven, 1903.