Page images

Lecoq, in enumerating the causes of rain, observes: "Enfin, on a remarqué que la végétation et surtout les grandes forêts attiraient les nuages et déterminaient souvent leur condensation1."

Another proof of the great influence which forests exercise upon meteorological phænomena is attested by the local distribution of hail. It is well-known that insurance companies against hail demand for certain districts a higher premium than for others. Casalbero, in the Province degl'Irpini in Naples, was protected towards the north-west by a forest against hail, and although occasional injury was done in the neighbourhood, Casalbero was free from it as long as the forest remained standing. It was however cut down, and the ground it formerly occupied was put under cultivation. Since that time the environs suffer almost annually from hail. Trifling as the cause appears, it may be productive of great effects. A damp forest, a marshy meadow, produces cloudy vapours: they accumulate, and the moist hot air in which the cloud floats, is condensed by the shade which that pigmy cloud produces.

A kind of vapour resembling steam is sometimes observed to hover early in the morning over ponds, or to rest upon hill sides. The latter spectacle may be frequently observed over Gunhill, the cliffs in St. John's, and near other rocky walls. The warmer air of the hill-side is cooled, a difference of temperature arises in the ascending current by coming in contact with the colder rocks, and the vapours become visible. I have been quite astonished to see the effects of this rapid cooling and condensation in the parish of St. John, chiefly while staying at the parsonage, where the warmer air from the sea in its ascent is rapidly cooled by the cliffs. I have repeatedly watched these fogs, which are scarcely known in the valley; and which sometimes were so thick, that it was impossible to see objects at a distance of fifty yards2.

It is a circumstance well-known in Barbados that the estates on the cliff have more rainy days in the course of the year than those in the valley. A certain apathy which would fain pronounce all scientific researches frivolous, has hitherto prevented our possessing any data as to the amount of this difference. A different spirit appears to have spread over Barbados, and it is much to be hoped that meteorology, one of the most important sciences of physics, may likewise profit by it.

I would not have it understood that I consider the quantity of rain

1 Elémens de Géographie Physique et de Météorologie, par H. Lecoq, p. 514. 2 It must have been frequently observed during winter, in the drawing-rooms of the rich and opulent, where groups made of marble, bouquets of artificial flowers, &c. ornament the chimney-piece, that the glass bells which cover the first are entirely covered on the inside with moisture, while those of the artificial flowers are free from it. The warmer air from the fire ascends and finds its way into the glass bell, where, coming in contact with the cold marble, it is condensed to saturation. This is a picture on a small scale which Nature offers on a larger, and which, as in this instance, the cliffs of St. John's in Barbados prove.

from the same cloud is greater in the upper parishes than it is in the lower. Experience proves the contrary. If we ascend a mountain of some height during rain, it will be found that the higher we rise, the smaller become the drops. The accurate observations at the Paris Observatory prove that the quantity of rain in the court-yard was one-ninth part more than on the terrace, which is about 92 feet above the ground. It is generally assumed that rain-drops on their descent increase in size, and this is said to be chiefly the case under the tropics. I have read of rain-drops which were an inch in diameter and produced a peculiar sensation in falling upon the skin. My experience during fourteen years under the tropics, from 18° N. latitude to about two degrees south of. the equator, and under the moist atmosphere of the equatorial forests, does not give me an instance where I would have estimated the drops of rain a quarter of an inch in diameter.

It is asserted that there is at present much less rain in Barbados than there was formerly, and many of the inhabitants ascribe it to the unlimited clearance of forest and brushwood; and although we have no direct reasons to prove why such clearances lessen the annual quantity of rain, we have abundant proof that it is so. In every instance, and in every part of the globe where forests have been cleared, a diminution of aqueous precipitations has been noted; and as it is a fact which remains uncontested that Barbados within the last fifty years was much more wooded than it is now, the diminution of rain must likewise be expected as the natural effect. The evidence of Humboldt, Leopold de Buch, Daniell, Dove and others, is so powerful on this subject, that I should wish to press particularly upon the attention of the reader how important the existence of wooded spots becomes to the agriculturist. I cannot do better than quote the words of Humboldt to enforce my own view: :- -"By felling the trees that cover the tops and the sides of mountains, men in every climate prepare at once two calamities for future generations-the want of fuel, and a scarcity of water. Trees, by the nature of their perspiration, and the radiation from their leaves in a sky without clouds, surround themselves with an atmosphere constantly cool and misty1.”

'Humboldt's Personal Narrative, English translation, vol. iv. p. 143. I would likewise draw the attention of the reader to the very pertinent remarks of Mr. Montgomery Martin, in the British Colonial Library, vol. v. p. 38.




THE month of January is one of the most delightful in the year. The sky is of a deep azure, and the breeze which sets in at an early hour seldom allows the thermometer to rise above 81° Fahr. It is generally dry; and it may be considered to be one of the most healthful in the course of the


February partakes of the same character; occasional showers refresh the air, and the thermometer ranges from 71° to 82°. Dr. Hillary, in his meteorological observations during the year 1755, observes that he saw Fahrenheit's thermometer in this month, in the mornings, at 70°, which he never observed before or since during the period of eleven years. According to the observations of that author, the month is generally healthful.

March is dry. According to Mr. Young's meteorological observations the least quantity of rain falls during this month, and a similar character is given in Hillary's time. The thermometer ranges from 72° to 83° Fahr. Slow nervous fevers, catarrhs, &c., appear to set in towards the end of it.

In April, dry warm weather prevails; occasional showers refresh the air, but the general character of the month is dryness. Sudden changes of temperature render this month less healthy than the previous one.

The commencement of May is dry and warm, but towards the latter end frequent showers fall, and heavy rains set in. The thermometer ranges from 74° to 86° Fahr.

In June the clouds are heavy; coruscations, lightning followed by thunder set in; frequent showers, but seldom heavy rains occur in the latter part of the month. Hillary speaks of the prevalence of putrid, bilious and depuratory fevers during this month. The thermometer ranges between 72° and 85°.

July is sultry and oppressive; vast masses of clouds rise on the horizon, and the wind is frequently from the south-west and west. This month brings in its train severe lightning followed by loud peals of thunder, at other times the rain descends in torrents; the heat and stillness of the air are quite oppressive: the thermometer varies between 76° and 86°. With the change of the weather, dysenteries become more frequent, and are sometimes epidemical. This refers chiefly to the coloured labourers. Infectious hooping-coughs have likewise been known to prevail during

this and the following month. The July of 1754 appears to have been an exception; the weather was cool and healthy during this month.

August is not so wet as the preceding month. There are frequent showers of rain, but they are not so heavy, and are intermixed with calm. hot days, with thunder and lightning. Calms and southerly winds, if there be any breeze, prevail. The thermometer ranges from 74° to 86° Fahr.

September is very wet.

There may be a few intermediate days of hot and calm weather, but showers are more frequent. The wind is variable, and blows generally from the south. Dysentery and slow fevers continue. The thermometer varies between 77° and 85° Fahr.

October, chiefly in the commencement, is still sultry; showers and occasionally heavy rains take place. Towards the middle it becomes drier, and refreshing breezes generally set in after some thunder-storms, which it appears close the rainy season. The thermometer stands sometimes

in the mornings as low as 72°, and seldom rises above 84° Fahr. Very heavy rains have distinguished the month of November, and Mr. Young has registered as much as 12:11 inches in 1845. The winds are sometimes variable, and not unfrequently blow from the south-west. The air becomes cooler, and the thermometer ranges between 72° and 85° Fahr. Dysentery and catarrhal fevers are prevalent.

The last month of the year partakes much of the first; it is generally cool and dry; there are however exceptions, and it has been known to rain almost every day more or less during this month. Dr. Hillary observes that in December 1754 as much as 11.27 inches of rain fell. The brisk and cool winds from the north-east render it healthy1.

I much regret that a greater number of meteorological observations have not been at my command to deduce from them conclusions which, although they could not be considered infallible, might have proved of interest to the meteorologist. Dr. Hillary, in his observations on the changes of the air in Barbados, informs us that he registered every morning the thermometer and barometer at or before sunrise, and again between the hours of twelve and one o'clock at noon, and this work contains some very valuable observations from the year 1753 to May 1758. His barometer appears to have been a common portable one, and cannot be much relied on for exactness. A proof of this is given by his assertion that the mercurial column did not alter its height during a whole month. Mr. Young of Fairfield, in the parish of St. Philip, has for a number of years noted with great regularity the state of the thermometer,

1 Since the above has been in print, I have seen Mr. Young's meteorological table for December 1846. It appears it resembled much the December of 1754; it rained daily with the exception of the 30th, and the quantity which fell during the month amounted to 13:51 inches.


* Hillary's Observations on the Changes of the Air, &c., p. 51.

barometer, and the quantity of rain which fell each month; and likewise more recently the hygrometer, and the solar radiation. I have not been able to procure a perfect set of these useful observations, for which Mr. Young deserves the thanks of every person interested in meteorological phænomena, but I have been enabled to examine 487 of his observations', from which I deduce the following results.

Results of 487 Meteorological Observations in Barbados.


Barometer in English inches. Thermometer after Fahr...S


Maximum ..








[ocr errors]






Min. Mean. Max. Min. Mean.


75° 80°.527

It does not appear that the temperature has changed since Dr. Hillary made his observations which furnish the following general results.

29.9734 30.020 29.740 29-9177




General Result.





[blocks in formation]

87° Fahr.



77 to 86

76 to 87

76 to 86

76 to 85


Highest. Lowest.

inches. inches.















Greatest range of thermometer during these seven years 17°, and of the barometer 4 of an inch.

During these 487 days there were 252 days with more or less rain, and 235 days without rain. The whole quantity which fell during that

1 These observations comprise the months of June, July, August, September, November and December, 1843; January, February, March and April, 1844; April, May, June, July, August and September, 1846.

« PreviousContinue »