180 Geology, — Meteorology, 



Art, IV. Geology, 



To observe the Formation of Soils upon a small Scale. — Sir Humphrey 

 Davy has explained, in his Agricultural Chemistry^ how this takes place on 

 the surface of naked rocks by partial decomposition ; the growth of lichens 

 being succeeded by mosses, and, on their decay by the smaller plants. A writer 

 in the Verulam observes, " even in cities this may be done by observing the 

 successive steps by which the top of a brick wall, for example, becomes 

 covered with vegetation. First, there is the green incrustation, called Bys- 

 sus by Linnaeus, but recently proved by our friend, Mr. Drummond, of the 

 Cork botanic garden, to be the primary germination of several species of 

 mosses, such as Polytricha and Tortulae. When this decays, a very thin 

 stratum of vegetable earth is formed, which affords a scanty support for the 

 roots of the next year's crop of mosses, and in process of time soil is formed 

 of a sufficient depth for Draba vdrna and other wall plants.'* 



Art. V. Meteorology, 



East Winds and Blights, April 50. 1828. — In conversation with Mr. 

 Gibbs of Brompton, he stated, that " we would certainly have an east wind 

 about this time." The wind had veered to the east in the morning of this 

 day, but at' the time we were speaking it had changed to the north-east. 

 He added, however, that for twenty-two years he had paid particular atten- 

 tion to this circumstance j and, except twice, always observed that the wind 

 blew from the eastward at the beginning of May. 



No one who has paid attention to the progress of vegetation in the vernal 

 months, but can remember how often they have had to witness the wither- 

 ing effects of the east wind on the tender plants, flowers, and shoots of this 

 season : its parching effects on the garden, and its hurtful consequences to 

 the young barley in the fields, are frequent complaints. These easterly 

 winds, too, are frequently attended by a blue mist, called, by those living to 

 the westward of the metropolis, " London smoke ;'* and though it is well 

 known, that the fuliginous vapour of this great city extends, like the train 

 of a comet, to the distance of fifty miles, yet that blue mist or haze, which is 

 known to be so extensive, cannot be occasioned by such a local circum- 

 stance. But from the want of simultaneous meteorological observations at 

 numerous distant stations, (a want which your Magazine is well de- 

 signed to remove), we have not sufficient data on which to form"a rational 

 opinion, as to the prevalence of either the east wind or the blue mist. 

 The latter is called a blight, and many people imagine that the aphides 

 are wafted through the air by this same mist ; because the depredations of 

 these insects become visible at the time, or soon afterwards : but with such 

 winds we have commonly a clear sky ; in course the sun's heat is intense, 

 and this it is which brings forth the insects from every place where they 

 were deposited in the previous autumn, and also instigates the pregnant 

 females to bring forth their incalculable generations. 



With respect to the direction of the wind at this period, 1 can only offer 

 an opinion which, I must own, rests on a very slender foundation. Having 

 had some acquaintance with the trade-winds of intertropical latitudes, and, 

 since my residence in England, having on many occasions been struck with 

 similar appearances, accompanied by easterly winds, I naturally conjectured 

 that such currents of air arose from the same cause, and that circumstances 

 of the state of the air, and of the general face of Europe, might temporarily 

 and occasionally produce those periodical winds observed by Mr. Gibbs. 

 — J,M, 



