OF GALILEO.

pull and lift vast stones, while the arms of a weak boy go on holding and gathering the other end of the same rope. The other is that of a simple but ingenious device found by a young relative of mine to be able to lower himself from a window with a rope without cruelly flaying the palms of his hands, as had happened to him a short time before to his very great injury. For easy understanding, I will make a little

A technical diagram of a vertical cylinder featuring a spiral groove carved around its body. A cord is shown resting within the groove, entering at point 'A' near the top and exiting at point 'B' near the base. The illustration demonstrates the mechanical device described for controlled descent.

sketch of it. Around a similar wooden cylinder AB, as thick as a reed and about a palmo palm, a unit of length long, he hollowed out a small canal in the form of a spiral of one and a half turns, and no more, and of a width capable of holding the rope he wanted to use; and this he made enter through the canal at the end A, and exit at the other end B, then surrounding such a cylinder and rope with a tube, also of wood or even of tin, but divided lengthwise and hinged, so that it could freely open and close: and then embracing and squeezing such a tube with both hands, the rope being recommended to a firm support above, he suspended himself on his arms, and such was the compression of the rope between the surrounding tube and the cylinder that, by squeezing his hands strongly at his will, he could sustain himself without descending, and by loosening them a little, he descended slowly at his pleasure.

Salu. A truly ingenious invention, and for a full explanation of its nature it seems to me I see, as if in shadow, that some other speculation could be added: but I do not want to digress further on this particular for now; especially as you wish to hear my thought concerning the resistance to tearing of other bodies, whose texture is not of filaments, like that of ropes and of the greater part of woods: but the coherence of their parts seems to consist in other causes, which in my judgment are reduced to two