IN excellence of climate, St. Helena is perhaps without an equal; no heat of torrid zones, or cold blasts from frigid regions, approach its genial shores. There no thunder-storms terrify the timid, no cholera, no yellow-fever, no small-pox, scarlatina, or deadly lurking fever-germs pollute the air. Nor is its balmy atmosphere ever marred by scorching winds, hot vapours, typhoons, hurricanes, cyclones, or any other characteristic of tropical regions. Throughout the year bright sunshine, clear skies, gentle breezes and deep blue seas, all combine to make it one of the most charming spots that can be found. The Island might reasonably and is generally supposed to be tropical in climate, lying as it does about one third of the way within the tropic of Capricorn, and only 955 miles from the Equator; but fortunately its isolated position, far removed from the influence of any large tract of land, immediately in the heart of the ever-prevailing fresh, healthy, south-east trade winds, completely frees it from any of the disagreeables which such a latitude might be expected to possess. The climate is also rendered more temperate than it would otherwise be, by the cool current of water which generally flows from the Antarctic regions towards the Island.; and when, on the other hand, the current sets in strongest from the Equatorial region—as it does when the rollers occur—it accounts for the close, oppressive, and warm state of the atmosphere on such occasions. Although not so much difference exists as in Europe, the year is really marked by four seasons—viz., Spring, extending from October to December; Summer, from January to March; Autumn, from April to June; and the remaining three months constituting Winter.
Although there is no perceptible difference for a week or so, Spring really commences on the 23rd September; Summer on the 22nd December, when the sun has its greatest south declination; Autumn on the 21st March, when the sun is on the equator; and
Winter on the 21st June, when the sun is furthest north. Twice during the year the sun is vertical—on the 5th February and the 6th November.
The length of day is very uniform throughout the year, the longest, occurring on December 21st, being thirteen hours two minutes' duration; and the shortest, the 21st June, being eleven hours eight minutes, exactly the opposite of what occurs in England. Spring is characterized by a minimum temperature of 55·5°, and a maximum of 68°, with bright, sunny, cheerful weather, occasionally varied by fresh and gentle showers; while the oaks, bursting out into full leaf, with gorse, mimosas, buddlea, and other plants, in full blossom, mingling their delicious perfumes with the fragrance of the newly-mown hay, give to the season much of the charming character of an English spring. Summer is marked by hotter weather, the thermometer reaching as high as 72·8° on the high land, and 82·6° in Jamestown. The vegetation of the lower land becomes scorched up, and heavy tropical rains occur about the month of March. The chief sign of autumn is the fall of the leaf, which occurs with the oak and some other exotic plants with as much regularity as it does in England, the temperature becoming less, with small drizzling rains, usually called Scotch mists, during the month of June. In the winter, the temperature falls to 53·2°, the weather becomes squall, wind and rain both increasing, until on the high land fires become not only bearable, but necessary, both for personal comfort and for the preservation of property from ruin by damp and mould. The climate of James' valley during the summer months is not agreeable; it is then and there that the only approach to really hot weather is experienced.
It is easy to imagine the indignation of some wayfaring visitor to Jamestown, after having passed—not slept, for sleep is often out of the question—a night there, restless from heat, and worried by mosquitoes ; but the climate of the town must not be considered in any way a type of that of the Island generally. The atmosphere of the town is so completely influenced by local circumstances, that it is altogether different from the rest of the Island. Built in one of those deep, narrow, water-cut ravines which transversely intersect the leeward coast, and enclosed between two huge basaltic hills, sloping up at angles of about 35° to a height of eight or ten hundred feet, it becomes, when the sun has heated them by day,
and they radiate that heat at night, a very oven on a large scale. The oppressiveness of the air is moreover increased. when occasionally the trade wind, falls, and a stagnant calm prevails perhaps for five or six days at a time, disturbed only by a gentle north-westerly air current, not strong enough to be called a wind, and at such periods the heat appears a great deal more intense than the maximum of 82·6° indicated by the thermometer, but this state of things never lasts long enough to produce unhealthiness. Whatever bad and injurious atmosphere accumulates is, before it has had time to promote evil, swept away by a fresh outburst of that pure and healthy South-east Trade so well deserving the title of "Doctor," which St. Helenians have given to it. The town is, moreover, naturally well drained and supplied with water, and it is not surprising to find that, with all its inconveniences during the summer months, Jamestown is not unhealthy. Permanent residents there suffer from relaxation, and its accompanying evils, and at times a low fever prevails to a small extent ; but this latter is chiefly confined to the very poor, and may be attributed to their poverty and mode of living, with insufficient food and comforts, rather than to any effect produced by climate.
As might be expected, the atmosphere* contains much moisture. Small islands, entirely surrounded by sea, must always be more or less damp, and this fact is as much against St. Helena as a residence for those who suffer from pulmonary complaints as Madeira. It has been observed that the pure African is more susceptible of such diseases than the native, but as very few instances of it occur at St. Helena at all, the large number of deaths which are registered must be attributed to seeds sown elsewhere.
Although the European garrison has until very recently been chiefly quartered in the town, statistics show that soldiers suffer less from mortality at St. Helena than at any other colonial station, and but a fractional degree more than in England.
The larger portion, or about four thousand, of the population, reside on the high land, or what is called the country, at altitudes varying from 1200 to 2000 feet. At this elevation, on the windward side, Longwood is situated; and at this spot, known to historians in connexion with the name of Napoleon Buonaparte, the only systematic meteorological observations which have been recorded were observed during the years 1840-45 by a detachment of Royal Artillery, under the direction of General Sir Edward
Sabine, R.A., F.R.S., and subsequently published. Longwood is itself a bleak, cold, exposed situation; and the complaints of Napoleon's staff against it as such were not without some reason. On this account it is perhaps not the most favourable spot for recording observations characteristic of the meteorology of the Island; still they may be taken as affording a tolerably correct record.
The building erected for these observations stands in. Lat. 15° 56' 41·2" S., Long. 5° 40' 31·5" W., at an altitude of 1764 feet above the sea, and about two and a half miles from it. The mean temperature of five years was 61·4°; the lowest being 52°, on the 5th September, 1845, and the highest 77·6°, on the 3rd March, 1842 ; the mean taking place at nearly equal intervals between—viz., early in June and about the middle of December. The mean height of the thermometer in the different months ranged from 57·07° in September to 66·24° in March, making an average difference of only 9·17° between the hottest and coldest months. The extreme range of thermometer being 25·6°, and the mean diurnal range 5·6°.*
Over many miles of ocean blows the South-east Trade, as pure a wind as is found on the face of the earth, sometimes accompanied by rain and sea-fog, and sometimes sweeping across the plains of Longwood and down the ravines with force enough to uproot trees and unroof houses, while many a sheltered glade in other parts of the Island experiences little of its fury. These strong Trades, with a force of 1·72 lbs.,† are the nearest approach to a storm that ever occurs at St. Helena. They are generally strongest in the months of September and October; and it is remarkable that at times while they blow with fury round the coast, even driving ships to sea from the snug anchorage on the leeward side, a perfect calm exists on the mountain ridge at Diana's Peak, only 2697 feet higher up.
Clouds often hang over the whole Island, high above the land, for several days together, giving rise to the local expression, "a covered day." They seem spread out over the land like a huge umbrella, as a protection to young verdure from the fierce rays of the sun.
Rainy seasons happen twice in the year—in summer and winter; the summer rains are heavy, the latter light and misty, but continuous. At each period heavy floods are likely to occur, doing considerable damage to gardens and roads, which latter are necessarily very steep.
* Appendix, pp. 396, 397.
† Appendix, p. 398.
On these occasions much of the surface soil, which, excepting in the hollows and ravines, scarcely extends to ten feet in depth, is also washed away; and trees, pigs, poultry, with other things, are occasionally carried down by the swollen mountain torrents to the sea. Such floods have long been noted, as the following extract from the records shows:—
"5 May, 1719.—On Saturday last there was such vast floods of water descended from about the middle of this Island as did abundance of damage, and wee think it was a water spout that broke about the main ridge because the water did not fall in shores after the usuall manner, but descended from the top of that bill with mighty floods and torrents. It carryed away the soile in an incredible manner with both grass, trees, yams, and stone walls before it. It brought down rocks of a mighty bulk, and covered abundance of fruitfull land wth stones, the fine earth being washt away in such great quantity's that the Sea for a great way round about the Island lookt like Black Mudd."
Although periodical seasons of great drought visit the island,* sometimes extending over four or five years at a time, the natural seasons, with abundance of rain, always return. The amount of rain which falls at the present time cannot account for the cuttingout of the ravines and valleys which exist, and it must, many thousand years ago, have been much greater. Most probably at that time the mountain tops were covered with snow, and the continual run of snow-water down to the lower land may have aided very considerably in cutting out those ravines.
The present amount of rainfall varies very much in different localities, and, as might be expected, very much less falls in Jamestown on the low coast than at Diana's Peak on the high mountain ridge. General Lefroy, R.A., recorded the following result of nine months' experiment:—
|Near Diana's Peak,||2644||ft. above the sea,||22·63||in. of rain.|
|A spot below ditto||1991||do.||27·11||do.|
Governor Beatson also recorded the average fall during four years,
* Great droughts occurred in 1713, 1724, 1738-39, 1747-48, 1752, 1759, 1772, 1779-80, and 1792. MSS. Records.
1810-13, at Plantation House, 1500 ft. above the sea, as 31.63 in. of rain.
And other records show that in the year 1862 the fall was
|at Ladder Hill on the||600||ft. above the sea,||18·85||in. of rain.|
|in James' Valley||250||do.||9·00||do.|
An average of thirty inches may be taken as a mean annual fall, but with so great a variation in different localities, it affords a figure of little value. The mean annual average at Longwood during five years was 47·19 inches, the greatest occurring in 1842, and the lowest in 1845, the former measuring 90·46, and the latter 19·41 inches.*
It has been considered that 140 days out of the year are rainy days; but the high central ridge is scarcely ever four-and-twenty hours without clouds resting on it, and distilling moisture.
Very little, indeed scarcely any, barometric pressure is exercised, but it is very systematic and regular. The mean pressure during five years at Longwood was observed to be 28·285 in. The greatest observed depression was 28·094 in., on the 14th March, 1843; and the greatest elevation 28·497 in., on the 9th July, 1842 : giving 0·403 in. as the extreme range. March, being the lowest month, showed a mean of 28·232 in. ; and July, the highest, 28·367 in. ; so that the range in the different months was 0·135 in. The mean diurnal variation being recorded at ·074 in. It has been noticed that during those months when the barometer is highest, the temperature is lowest, and when the barometer is lowest, the temperature is highest. The mean height of the barometer at the sea level, at Prosperous Bay, was 30·08 in.†
During five years the mean elastic force of aqueous vapour at Longwood was ·470 in.; the mean in the different months varied from a maximum of ·559 in. in March, to a minimum of ·411 in. in August. The range in the different months was ·148 in., and the diurnal range ·032 in.‡
The mean gaseous pressure, on dry air, obtained by deducting the elastic force of the vapour from the total barometric pressure, was found to be 27·816 in., with a minimum in March of 27·666 in., and a maximum in July of 27·948 in. The range in the different months was ·282 in., and the diurnal range ·074 in.§
* Appendix, p. 400.
† Appendix, p. 401.
‡ Appendix, p. 402.
§ Appendix. p. 403.
The mean degree of humidity of the air was 87.* There is a considerable difference between rainfall and evaporation ; and at Ladder Hill, 700 ft. above the sea, in the year commencing 12th, February, 1860, the excess was observed to be 81·42 in. It must be borne in mind, however, that the station where this was noticed is situated on the low land, near the sea coast, on the leeward side—a spot where comparatively little rain falls.
The rise and fall of tide is almost imperceptible, the maximum being, at times of new and full moon, only 2 ft. 10 in., and the establishment 2h. 9m. Perhaps the most remarkable of any phenomena connected with the Island is that known as The Rollers, or huge rolling waves, which have from time to time caused much loss of life and property, and which are as well known at Ascension as at St. Helena. The Rollers usually set in during the early part of the year; and the greatest and most destructive on record occurred in the month of February, I846. At St. Helena, on the 16th of that month, there was nothing unusual to attract the attention of the quiet inhabitants of the peaceful settlement of Jamestown, unless it was the marked stillness of the calm that prevailed, the S.E. Trade wind having entirely lulled for about ten days, leaving an oppressive sultry atmosphere. The barometer had risen rapidly, and stood high, and the atmosphere was dense and heavy, with thick clouds obscuring the sky. In the evening, towards sunset, a few waves commenced to break upon the beach in front of the town, but there was nothing very striking in this common occurrence. Through the night, however, the waves increased, and at daybreak on the following morning the surface of the spa opposite the town had assumed the appearance of a sheet of foam, broken only by tremendous waves, which came like so many rolling mountains chasing one another, carrying everything before them, and breaking near the shore. All this disturbance was within half a mile from the coast; the ships lying at anchor beyond that distance not being affected, while those within, some thirteen in number, including eleven captured slave ships, were, in the short space of seven hours, dashed into atoms. One of them, the Descobrador, a Brazilian brig of 127 tons burden, was with her anchors and cables literally lifted up, carried broadside on to the English schooner Cornelia, and both together driven on to the shore. So little notice
* Appendix. p. 399.
had been given that there was not even time to remove the shipkeepers who were on board of the slave ships. Some of them escaped to other ships in the roadstead ; but as the Descobrador struck the beach broadside on, and sea after sea broke over her, the keeper, with his wife and a Lascar servant, were seen holding on by the rails of the vessel, appealing for help. While they remained in this perilous position, Mr. Chatfield, of H.M.S. Flying Fish, attempted to gain the vessel with a rope, but was unable through the violence of the waves ; but, after an unsuccessful attempt to fire a rocket and line across the wreck, an American sailor, named Roach, had the satisfaction of reaching it. With a rope he lashed himself and the woman together, and jumping into the waves both were drawn to the shore. The keeper and the Lascar jumped overboard, and in a momentary lull were both also saved. Not ten minutes did the whole of this occupy, and scarcely was the work of destruction over, when another slaver was driven from her anchors on to the shore; and then another, a splendid yacht-built schooner, the Aquilla, followed immediately, both being in the space of one moment shivered into a mass of splinters against the rocks. Ere mid-day arrived the rollers increased in size all along the leeward coast, the water on the southern side of the Island remaining quite undisturbed, and ship after ship shared a similar fate. Two Brazilian schooners, the Enfranzia and the Esperanza, were engulfed by huge waves sweeping over them; one of them sunk where she was in an instant, while the other drifted out to sea a total wreck. But at one o'clock the biggest wave of all, a tremendous rolling mountain of water, came in towards the shore, with every appearance of sweeping everything, even the Island itself, away. So huge was it that all behind it, almost even the very light of the sun, was shut out from the terrified spectators. The roaring of these waves could be heard for several miles inland; and one gentleman, long resident there, told me that never before in his life had he been so frightened as he was when he saw them. In one of these enormous waves the English brig Rocket, of 230 tons, was lifted with her hull in a vertical position, her bows up, and her stern down, and as the wave broke not a single trace of her was seen. The scene of devastation was not at sea alone, for the same wave came rolling along the wharf, tearing down large iron watertanks and strongly-built iron cranes, one of which it carried fifty
yards or more into the coal-yard, and dashing with the utmost fury against the cliff carried away a balcony, which but half-an-hour before had been vacated by thirty or forty spectators. The whole scene is described as one of wild and awful grandeur; the sea and the shore being everywhere covered with broken boats, spars, casks, timber, all floating in one huge boiling surge. The glacis and the lines of Jamestown were impassable through wreck of every description scattered about: coal-yards, wharf, and sea walls, batteries and cannon, were swept down. At six o'clock in the evening no abatement occurred, and two other ships, the Quatro de Marco, which hitherto, held by four anchors, had withstood the fury of the sea, and the Julia, a Brazilian, were dashed to pieces on the west rocks. The destruction of these ships was as instantaneous as a child would crush a fragile toy. The former vessel was seen with masts standing, only a moment before she floated a thousand pieces in the surge. The latter was rolled over just as if the waves were playing at football or cricket with her, and eventually lodged high up on the west rocks against the cliffs of Ladder Hill. At Rupert's Valley the sea rolled inland a distance of 216 feet. Eleven of the destroyed ships were condemned slavers, and of no great value ; therefore the estimated damage done did not exceed 10,000l. This oceanic phenomenon occurs with greater force and more frequency at the Island of Ascension, in lat. 7° 581/2' S., and long. 14° 231/2' W., where communication between ships and the shore is completely stopped for a week or more at a time. Through the kindness of Captain Wilmshurst, R.N., I was able during the year commencing September, 1867, to make a comparison of the time and force of the rollers at each Island.* It appears that they set in at Ascension, upon the average, one to seven days sooner than they do at St. Helena, and that their course is south or south-easterly from the Equator, breaking against the northern shores only of both Islands. Although they happen at any period of the year, they appear chiefly in the months of December to March, usually occurring with greatest force in February.†
* Appendix. p. 404.
† Extracts from MSS. Island Records:—
"16 Jany. 1710/11.—The Governor reports that the high seas which began the 13th of this Instant and continued the 14th and 15th, has done a great deale of damage, it has intirely washed away the lower fort of two guns at 'Bankses,' and had like to wash the
Popular opinion has ascribed the cause of the Rollers to distant submarine volcanic action, but they occur with too much regularity to admit this reason, and I believe them to be due to oceanic currents, influenced by atmospheric pressure; in fact, a return wave, caused by the meeting of the Antarctic waters with the great Equatorial current of the Gulf Stream, and influenced by the North-east Trade winds. It is during the Roller months that the sun has greatest power in the Tropical Southern Hemisphere, and therefore the greatest amount of evaporation takes place ; consequently the flow of cold water from the Antarctic regions towards the Equator is then most abundant and most rapid; as this current gets well warmed by the time it approaches the Line, it is hotter than the water of the great Equatorial current flowing south round Cape Verde, which it meets in latitude 4° South. These waters coming into violent collision, and not readily mixing because of difference in temperature, must result in a return current either northward or southward. This return takes place in the latter direction, after the Equatorial current has been forced to flow out on either side against the Brazilian and the African continental coasts.* The Equatorial current being at its maximum of strength at this period of the year is to a great extent due to the influence of the North-east Trade winds upon it, for it is their period of greatest force and most southern latitude. During the months of December to May the Equatorial limit of the North-east Trades is 5° to 7° N. lat., ex-
guns away, for we had enough to do to save them. The same high seas has also
broke the middle angle of the Trench in James Valley for a matter of one hundred and ten foot,
and has damaged the angle where the round tower is of one gun insomuch as it was like to tumble
down.—These high seas sunk the punt and broke her loose, also the yaul, and nearly washed down
"5 April, 1715.—We think that a ship that arrives here about Christmas cannot possibly be dispatched in less than a month, because of the very great surfes that usually happens about that time of the year. We are informed that the latter end of March and beginning of April is also a time when abundance of high seas do usually happen, and we are the more confirm'd in such an opinion because the Honble: Companies long boat wch brought cutt stone from Sandy Bay, wch is at the Windermost part of the Island, has been laden these nine days, and is still loaden at a grapling in this road, but the surf is so high and violent that we dare not attempt to unload her, neither with these seas is it possible that any boat with safety can come to the crane to be unlivered."
"12th April, 1715—This being the first day the Surfe abated the long boat was dispatched again for Sandy Bay, and the Governor mencond it that it might appear what great seas we have sometimes, but especially at this time of year, for now the great seas have held nineteen days, and the long boat was unloaden with much difficulty by smaller boats."
Rollers are also referred to as having occurred in March, 1717; December, 1733; February, 1720; and April, 1743.
* Maury, Phys. Geo. of the Sea, p. 383, § 892.
tending as far as 2° N. in February and March; while for the rest of the year they only reach as far as 10° 62' N.* Their proportionate force is also during the same periods, between the parallels of 10° to 15° N. lat., as 7.41 to 4.83.†
Some idea of the enormous force with which these waters meet and send back the Anctarctic current against the shores of Ascension and St. Helena, may be obtained from the following extract from Admiral Semmes' Voyages:‡—
"For the next few days, we encountered a remarkable easterly current, the current in this part of the ocean being almost constantly to the westward. This current, which we were now stemming—for we were sailing towards the north-west—retarded us as much as fifty miles in a single day! So remarkable did the phenomenon appear, that if I had noticed it but for a single day I should have been inclined to think that I had made some mistake in my observations or that there was some error in my instrument; but we noticed it day after day for four or five days.
"Contemporaneously with this phenomenon, another and even more wonderful one appeared. This was a succession of tide-rips, so remarkable that they deserve special description.
"The Sumter lay nearly stationary during the whole of these phenomena, the easterly current setting her back nearly as much as she gained under sail. She was in the average latitude of 5° N., and average longitude of 42° W. For the first three days, the rips appeared with wonderful regularity, there being an interval of just twelve hours between them. They approached us from the south, and travelled towards the north. At first only a line of foam would be seen on the distant horizon, approaching the ship very rapidly. As it came nearer, an almost perpendicular wall of water, extending east and west as far as the eye could reach, would be seen, the top of the wall boiling and foaming like a breaker rolling over a rocky bottom. As the ridge approached nearer and nearer, it Assumed the form of a series of rough billows, jostling against and struggling with each other, producing a scene of the utmost confusion, the noise resembling that of a distant cataract. Reaching the ship, these billows would strike her with such force as to send their
‡ My Adventures Afloat. By Admiral Semmes.
spray to the deck, and cause her to roll and pitch as though she were amid breakers. The phenomenon was, indeed, that of breakers, only the cause was not apparent, there being no shoal water to account for it. The Sumter sometimes rolled so violently in these breakers when broadside to, that we were obliged to keep her off her course several points to bring the sea on her quarter, and thus mitigate the effect. The belt of rips would not be broad, and as it travelled very rapidly—fifteen or twenty miles the hour—the ship would not be long within its influence. In the course of three-quarters of an hour it would disappear entirely on the distant northern horizon. So curious was the whole phenomenon, that the sailors as well as the officers assembled, as if by common consent, to witness it. 'There come the tide-rips!' some would exclaim, and in a moment there -would be a demand for the telescopes, and a rush to the ship's side to witness the curious spectacle. These rips have frequently been noticed by navigators, and discussed by philosophers, but hitherto no satisfactory explanation has been given of them. They are like the bores at the mouths of great rivers—as at the mouth of the Amazon, in the Western Hemisphere, and of the Ganges in the Eastern—great breathings or convulsions of the sea, the causes of which elude our research. These bores sometimes come in, in great perpendicular walls, sweeping everything before them, and causing immense destruction of life and property. I was at first inclined to attribute these tide-rips to the lunar influence, as they appeared twice in the twenty four hours, like the tides, and each time near the passing of the meridian by the moon; but, in a few days, they varied the times of their appearance, and came on quite irregularly, sometimes with an interval of five or six hours only. And then the tidal wave, for it is evidently this, and not a current, should be from east to west, if it were due to lunar influence; and we have seen that it travelled from south to north. Nor could I connect it with the easterly current that was prevailing, for it travelled at right angles to the current, and not with or against it. It was evidently due to some pretty uniform law, as it always travelled in the same direction."