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much violence as to be even dangerous to vessels. On the supposition that the course of the trade-wind is an ascending one, it might be expected in autumn to cease to blow at heights some days before it ceased on the sea shore, progressively descending in height as the northern limit of the wind at the surface of the sea approached the island; and such is found to be the fact. The S.W. wind, which takes the place of the trade-wind as the latter ceases to blow, is observed in all years to descend progressively from those highest points, on which, as has been remarked, it prevails throughout the year. Its descent is traced by the clouds, which, in October, veil the south side of the Peak of Teneriffe; sinking slowly, they rest on a ridge of mountains, between Orotava and the southern coast, six thousand feet in height, where they break in dreadful storms. It is a full week, and sometimes even more, before the S.W. wind is felt on the sea coast, where it prevails for months afterwards, whilst it rains on the declivity of the moun tain, and snow is on the Peak. A remarkable fact, viewed in this connexion, is the greater height of the barometer in the summer months, when the opposite currents are prevailing over the island, than in the winter months, when the S.W. alone prevails. The mean of Don Francisco Escolar's register, kept during three years, gives, for the months of winter and summer respectively, as follows, the heights of the column of mercury being reduced for temperature.

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or rather more than one-tenth of a British inch.

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1.156

The island of Grand Canary presents a remarkable peculiarity in the progression of its mean monthly temperature, which is highly worthy the attention of meteorologists. The following table exhibits the result of a register kept at Las Palmas, during ten years, by Dr. Bandini de Gatti. The time of observation was daily at noon; from whence the results inserted in the first column are immediately derived those in the second column are the approximate mean temperatures, derived from the observations at noon, by presuming the same

difference to exist, which has been already stated to have been observed at Santa Cruz between the temperature of noon, and that of the mean between noon and sunrise.

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By this table it is seen that the maximum of heat takes place at Las Palmas in October instead of August; that as far as September the progression is regular, and accords with the register of Santa Cruz; but that, instead of diminishing in September and October, as is usual from the decreasing southern declination of the sun, the heat, on the contrary, continues to augment, until in the middle of October it attains a height only known in the hottest tropical climates. The general understanding of the inhabitants corresponds with the register; and the peculiarity of the climate is marked, as might be expected, by a corresponding peculiarity in the vegetation. Thus the Palm-trees, from which Las Palmas takes its name, and which flourish greatly in its vicinity, yield ripe dates in abundance; whereas the few trees of the same kind which are found in Teneriffe do not ripen fruit. The Euphorbia Balsamifera, which requires a great deal of warmth, is found in the neighbourhood of Las Palmas, as high as eight hundred feet, forming bushes ten or twelve feet high; whereas at Santa Cruz, and at Oratava, it hardly rises above the ground. Nearly the same may be said of the Plocama Pendula. The gardens of Canary are adorned with East and West India trees, not seen in Teneriffe; Poinciana Pulcherrima, of uncommon size and beauty; Bixa Orellana and Tamarind trees, as large as the Lime-trees of Europe. A magnificent avenue of the large trees of the Carica Papaya, or Papaw tree, is found in the hospital of

St. Lazarus; all these testify that, during a part of the year at least, Canary is subject to a degree of heat peculiarly intense.

Mr. von Buch attributes this remarkable peculiarity in the climate of Grand Canary to the cessation of the trade-wind in September, when a period of calms intervenes before the southwest wind is steadily established; during these calms, the atmosphere near the island, being undisturbed by the local winds which prevail at the same period at the other islands, becomes greatly heated by the effects of solar radiation, to which the peculiar form and geological character of the island conduce in a more than ordinary degree. It is, we believe, the first phenomenon of the kind that has been noticed, and is highly curious as a meteorological fact, as well as in regard to the influence of climate on vegetation.

Temperature of Springs and Fountains in Teneriffe.—It has been already observed, that the rains take place only in the winter months, from November to March; but during the summer months there is a constant precipitation from nine or ten in the morning to five in the evening, in the region of forests, at the elevation of from 2500 to 4100 feet. From whichever of these sources we suppose the springs or fountains, to be supplied, it is reasonable to expect that the temperature of those that are found near the level of the sea should be colder than the mean temperature of the year at that level. Accordingly, it appears that the average temperature of the following springs, ascertained by M. von Buch, is 14.25 R., or 64.1 Fahr., whilst the mean temperature of the year, as shown by Escolar's observations, is 17.3 R., or 71. Fahr. ; or, on the average, the temperature of the springs near the level of the sea is 7° Fahr. colder than the mean temperature of the air during the year.

6th May.—An uncommonly fine and copious spring,

gushing out from under a bed of lava, at Cape
Martianez, under La Paz, near Oratava

This temperature is permanent throughout the
year.

8th May. The spring" del Rey," between Realexo

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14.2 R.

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6th Sept.-The same spring

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1st June. Very copious springs, gushing out like waterfalls from the rocks beneath the mill of

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Gordaxylo, near Realexo

6th Sept The same spring

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Up to the height of 2000 feet above the sea the temperature of the springs, generally, suffers scarcely any sensible diminution; consequently the mean temperature of the air in ascending gradually approaches that of the springs. Above 2000 feet, and between that height and the commencement of the forest region, the springs diminish considerably and rapidly in temperature all round the island, as is shown by the following examples :

August.-Agua de las Mercedes, 2200 feet, in the wood of Obispo above Laguna, under gigantic laurels

- 11.2 R.

Sept.-Fuente de Vero, and Fuente de los Villanos,

2800 feet

June. A spring near the hermitage of Esperanza,

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2100 feet August.-Fuente Guillen, a spring between Esperanza and Matanha, 2565 feet

May. A copious fountain in the rocks above Realexo ariba, 2600 feet

10.6

12.2

12.1

11.9

May and June. A spring on the mountain of Ti-
gayga, 2000 feet
May and June-A spring on the left side of the Ba-

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ranco, leading to Rambla, 2000 feet At the commencement of the forest region, therefore, the average temperature of the springs may be considered as 11° R. or 3° less than at the level of the sea. From that height to the upper limit of the forest region, where the precipitation furnishes a constant supply, the water in deposits differs little from the temperature of the air; and above that region, the springs are too few, and too inconsiderable, to preserve an independent temperature.

E. S.

131

On a Figured Variety of Coal, occurring in the Coal-field of Glamorganshire; in a Letter to the Editor.-By J. MAC CULLOCH, M.D. F.R.S.

DEAR SIR,

I was not aware that the singular variety of coal, to which the title of this letter alludes, was unknown to mineralogists, or I should not so long have delayed sending you this notice of a peculiarity, which, independently of the difficulty which it presents, offers a fact deserving of regard in the history of this interesting substance. I must presume, that it has never yet occurred elsewhere, than in the place whence the specimens, which I have seen, were procured; because a form so remarkable could not have failed to attract the attention

workmen, and would, therefore, have, ere now, been brought before the attention of mineralogists. Should it merely have been overlooked in other coal deposits, the present public notice may serve to call attention to it; and, perhaps, also induce mineralogists, as well as workmen, to examine more narrowly into a substance, which, in spite of its importance and familiarity, must have been strangely neglected, when such doctrines respecting its chemical nature, as those of Mr. Kirwan, and respecting its chemical origin, such as those of Sir James Hall, and Playfair, could have been received, without question, for so long a time, and entertained as truth till they were corrected, at so very late a period, by my own examination of bituminous substances, appended to the Essay on the Distillation of Wood, in the Geological Transactions.

The variety, to which I allude, has been frequently found in the coal works about Merthyr Tidfil, and, indeed, may be said to occur almost daily; but how widely it may extend through this coal basin, there are no means of knowing. It would be superfluous to describe, either the nature of this coal-field, or of the coal itself, since both are familiarly known; it may be sufficient to remind your readers, that it is a dry coal, though not, in this respect, of a very highly defined character; while I hope that they are already aware, from the paper to which I have alluded, that there are no definite varieties of coal, as is commonly supposed, in consequence of certain misleading and

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