Ustulago, when the fruit instead of seed produces a black powder, as in barley, oats, &c. To which perhaps the honey-dew ought to have been added, and the canker, in the former of which the nourishing fluid of the plant seems to be exsuded by a retrograde motion of the cutaneous lymphatics, as in the sweating sickness of the last century. The latter is a phagedenic ulcer of the bark, very destructive to young apple- trees, and which in cherry-trees is attended with a deposition of gum arabic, which often terminates in the death of the tree.] [_Ergot's horn_. l. 513. There is a disease frequently affects the rye in France, and sometimes in England in moist seasons, which is called Ergot, or horn seed; the grain becomes considerably elongated and is either straight or crooked, containing black meal along with the white, and appears to be pierced by insects, which were probably the cause of the disease. Mr. Duhamel ascribes it to this cause, and compares it to galls on oak-leaves. By the use of this bad grain amongst the poor diseases have been produced attended with great debility and mortification of the extremities both in France and England. Dict. Raison. art. Siegle. Philosop. Transact.] [_On glass unneal'd_. l. 519. The glass makers occasionally make what they call _proofs_, which are cooled hastily, whereas the other glass vessels are removed from warmer ovens to cooler ones, and suffered to cool by slow degrees, which is called annealing, or nealing them. If an unnealed glass be scratched by even a grain of sand falling into it, it will seem to consider of it for some time, or even a day, and will then crack into a thousand pieces. The same happens to a smooth surfaced lead-ore in Derbyshire, the workmen having cleared a large face of it scratch it with picks, and in a few hours many tons of it crack to pieces and fall, with a kind of explosion. Whitehurst's Theory of Earth. Glass dropped into cold water, called Prince Rupert's drops, explode when a small part of their tails are broken off, more suddenly indeed, but probably from the same cause. Are the internal particles of these elastic bodies kept so far from each other by the external crust that they are nearly in a state of repulsion into which state they are thrown by their vibrations from any violence applied? Or, like elastic balls in certain proportions suspended in contact with each other, can motion once began be increased by their elasticity, till the whole explodes? And can this power be applied to any mechanical purposes?]