I have stated that the drills formed by the Suffolk drill-machine are very shallow; they are merely sufficient to afford about an inch of covering to the grain; but I have been assured by the best judges that the natural tendency of the cereal grains to strike their fibres is such that a heavy covering is unnecessary. Our national opinion is in favour of a heavy covering, and our wheat especially is actually imbedded deeply in the ground with a plough.
The practice in Great Britain universally is to harrow in the grain. The same practice is universally prevalent in France, where the land is left roughly harrowed (in the case of winter wheat), in order that the mouldering of the clods in spring may afford a kind of earthing to the plants, and prevent the running together of the earth in the wet winter months, as is too frequent on tenacious soils too finely harrowed.
It is not very long since the advantage of compressing the soil, for wheat in particular, was discovered in Buckinghamshire, by the accidental circumstance of a roller (which had been used for some different purpose) having been drawn in a zig-zag direction across a wheat field. The plants tillered better, looked far more vigorous during their advance to maturity, and yielded a far better return on the part of the field so distinguished by the course of the rollers, which soon after became a favourite implement in the culture of grain crops.
There is no doubt that all seeds are frequently sown with wasteful prodigality, because they are cheap or indifferent in quality. How much better then is it to have those of superior quality, though at a higher price, and to encourage the distribution of them in the soil by a careful mode of sowing!
Grains of corn of superior excellence are frequently selected with great care, as by Colonel le Couteur, in Jersey, and then sown with a dibble in seedling beds. The plants thus carefully treated tiller surprisingly, and produce accordingly; after two or three seasons, a fine variety, or a renovation of some previously established one, is obtained, and the seed is anxiously sought for.
Do any of our farmers ever dream of going through their corn fields in harvest, and thus obtain choice seeds? And yet what is there to prevent success in this respect? A poor farmer who cannot afford to purchase celebrated varieties at a high cost, may become his own seedsman, by care and assiduity, in an incredibly short time. Let some of our readers make the desired experiments for their own sakes.
SUSPENSION BRIDGES.
On the Theory of Suspension Bridges, with some account of their early history. By Mr G. F. Fordham. Head at the Scientific Society, March 12, 1840.
Suspension Bridges appear to be of very ancient origin: travellers have discovered their existence in South America, in China, in Thibet, and in the Indian peninsula. They are most frequently met with in mountainous regions, and being suspended across a deep ravine, or an impetuous torrent, permit the passage of the traveller where the construction of any other kind of bridge would be entirely impracticable. Humboldt informs us that in South America there are numerous bridges of this kind formed of ropes made from the fibrous parts of the roots of the American agavey (Agave Americana). These ropes, which are three or four inches in diameter, are attached on each bank to a clumsy framework composed of the trunk of the Schinus molle; where, however, the banks are flat and low, this framework raises the bridge so much above the ground as to prevent it from being accessible. To remedy this inconvenience, steps or ladders are in these cases placed at each extremity of the bridge, by ascending which all who wish to pass over readily reach the roadway. The roadway is formed by covering the ropes transversely with small cylindrical pieces of bamboo. The bridge of Penipé erected over the Chamboo is described as being 120 feet long and 8 feet broad, but there are others which have much larger dimensions. A bridge of this kind will generally remain in good condition 20 or 25 years, though some of the ropes require renewing every 8 or 10 years. It is worthy of remark, as evincing the high antiquity of these structures, that they are known to have existed in South America long prior to the arrival of Europeans. The utility of these bridges in mountainous countries is placed in a striking point of view by the fact mentioned by Humboldt, of a permanent communication having been established between Quito and Lima, by means of a rope bridge of extraordinary length, after 40,000l. had been expended in a fruitless attempt to build a stone bridge over a torrent which rushes from the Cordilleras or the Andes. Over this bridge of ropes, which is erected near Santa, travellers with loaded mules can pass in safety.
But suspension bridges composed of stronger and more durable materials than twisted fibres and tendrils of plants, are found to exist in these remote and semi-barbarous regions; in Thibet, as well as in China, many iron suspension bridges have been discovered, and it is no improbable conjecture that in countries so little known and visited by Europeans, others may exist, of which we have as yet received no accounts. The most remarkable bridge of this kind of which we have any knowledge in Thibet, is the bridge of Chuka-cha-zum, stretched over the Tehintchieu river, and situated about 18 miles from Murichom. Turner, in his Embassy to the Court of Thibet, says, “Only one horse is admitted to go over it at a time: it swings as you tread upon it, re-acting at the same time with a force that impels you every step you take to quicken your pace. It may be necessary to say, in explanation of its construction, that on the five chains which support the platform, are placed several layers of strong coarse mats of bamboo, loosely put down, so as to play with the swing of the bridge; and that a fence on each side contributes to the security of the passenger.” The date of the erection of this bridge is unknown to the inhabitants of the country, and they even ascribe to it a fabulous origin. The length of this bridge appears to be about 150 feet.