Sir John Leslie used to attribute the stability of this tower to the cohesion of the mortar it is built with being sufficient to maintain it erect, in spite of its being out of the condition required by physics--to wit, that "in order that a column shall stand, a perpendicular let fall from the centre of gravity must fall within the base." Sir John describes the column of Pisa to be in violation of this principle; but, according to designs shown to Dr. Cumming, at Pisa, in 1836, the perpendicular does fall within the base. ----- Footnote 2: When at Pisa, many years since, Captain Basil Hall investigated the origin and divergence of the tower from the perpendicular, and established completely to his own satisfaction that it had been built from top to bottom, originally, just as it now stands. His reasons for thinking so are, that the line of the tower, on that side towards which it leans, has not the same curvature as the line on the opposite, or what may be called the upper side. If the tower had been built upright, and then been made to incline over, the line of the wall on that side towards which the inclination was given, would be more or less concave in that direction, owing to the nodding or "swagging over" of the top, by the simple action of gravity acting on a very tall mass of masonry, which is more or less elastic when placed in a sloping position. But the contrary is the fact; for the line of wall on the side towards which the tower leans, is decidedly more convex than the opposite side. Captain Hall has, therefore, no doubt whatever that the architect, in rearing his successive courses of stones, gained or stole a little at each layer, so as to render his work less and less overhanging as he went up; and thus, without betraying what he was about, really gained stability. ------------------ HOLDING A "CRAWS' COURT." Dr. Edmonston in his interesting "_View of the Zetland Islands_," relates that the hooded Crow sometimes engages in merry meetings, but, savage-like, concludes by a sanguinary sacrifice. The crows generally appear in pairs, even during winter, except when attracted to a spot in search of food, or when they assemble for the purpose of holding what is called a _Craws' Court_. This latter institution exhibits a curious fact in their history. Numbers are seen to assemble on a particular hill or field, from many different parts. On some occasions, the meeting does not appear complete before the expiration of a day or two. As soon as all the deputies have arrived, a very general noise and croaking ensue; and shortly after, the whole fall upon one or two individuals, whom they persecute and beat until they kill them. When this has been accomplished, they quietly disperse. ------------------ ALPINE PERILS.