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.