Page images
[ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][merged small]
[merged small][ocr errors]
[ocr errors]

plumbago, which is intermediate between

the diamond and charcoal, as to the quantity of oxygen absorbed in combustion, and the heat required for this process. The carbonaceous mineral anthracolite, or carburet of alumine, resembles plumbago in this respect. Therefore the author concludes, that diamond is the pure carbonaceous principle ; and this in a low degree of oxygenation produces plumbago, anthracolite, and the different species of difficultly combustible coals; in a higher degree, common charcoal; and in complete oxygenation, carbonic acid. Of these, the purest carbone is that which requires the highest heat for combustion ; and therefore diamond and plumbago, even when fully ignited, cannot continue to burn when the igniting heat is removed. This disficulty of oxygenation resembles that of azote, which, when pure, requires the ele&tric spark, or some very powerful agent, to produce oxygenation; but when

partly oxygenated in the form of nitrous gas, requires only the mere contaët of oxygen to produce a full saturation. CHAPTAL has given an interesting Memoir on the method of cultivating the mountains of Cevennes. This chain of mountains, naturally dry and sterile, with steep and rugged banks, has been converted, by the industry of the natives, into fertile gardens and plantations, furnishing abundance of support for two or three hundred thousand inhabitants. Their inge. nuity and industry is particularly shewn in the method which they employ to fill the deep gullies or ravines which are formed by the violence of the mountain torrents washing away all the loose soil on the fides of the hills, and laying bare the naked rock. To fill up a ravine the inhabitant of Cevennes begins by building a stone wall without mortar at the foot of the mountain across the whole breadth of the ravine, from three to fix feet in height, according to its depth. This wall forms a dyke, which breaks the force of the torrents, and suffers the water to escape, while it detains the earth and fragments of stone which are carried with it. The effe&t of this is gradually to fill up the lower part of the ravine by the deposition from the streams which descend from the mountains. Then another wall, similar to the former, and parallel to it, is built higher up within the inner angle of the ravine, which has the fame effect as the first. In this manner he proceeds with successive parallel walls even to the top of the mountain; and the ravine is thus converted into beds of good soil, rising in stages the one above the other, and capable of excellent culture. The mountain streams being thus made to flow upon more level ground are broken in their force, and no longer ravage the plains by their impetuous fury, but serve the beneficial purpose of constantly watering the fields which have been won by this ingenious industry. The cultivator then plants his stages of mulberry-trees upon these platforms, sows his maize, potatoes, legumes, and grain of every kind; and

with prudent economy plants his vines on

the upper fide of the walls, and trains them over to the lower fide that they may not occupy that room in his artificial fields

which can be filled with other crops. His

[ocr errors]
[ocr errors]
[ocr errors][ocr errors][ocr errors][ocr errors]
[merged small][merged small][merged small][merged small][ocr errors][ocr errors][ocr errors][ocr errors]
« PreviousContinue »