visibly the whole weight about nine inches, which suddenly dropping, made a great heap of ruins in the place, without scattering or accident. It was half a minute before the heap already fallen opened in two or three places, and emitted smoke. By this successful experiment, the force of gunpowder may be ascertained; eighteen pounds only of which lifted up a weight of more than three thousand tons, and saved the work of a thousand labourers. The fall of so great a weight from a height of two hundred feet gave such a concussion to the ground, that the inhabitants round about took it for the shock of an earthquake." ------------------ SNOW SPECTACLES. Ellis, in his _Voyage to Hudson's Bay_, written in the middle of last century, says of the Esquimaux:--"Their snow eyes, as they very properly call them, are a proof of their sagacity. They are little pieces of wood or ivory, properly formed to cover the organs of vision, and tied on behind the head. They have two slits, of the exact length of the eyes, but very narrow; and they see through them very distinctly, and without the least inconvenience. This invention preserves them from snow-blindness, a very dangerous and powerful malady, caused by the action of the light strongly reflected from the snow, especially in the spring, when the sun is considerably elevated above the horizon. The use of these eyes considerably strengthens the sight, and the Esquimaux are so accustomed to them, that when they have a mind to view distant objects, they commonly use them instead of spy-glasses." ------------------ A SELF-TAUGHT MECHANIST.