The values of “Young’s modulus” were determined for several metals by a method devised by Sir W. Thomson. According to this method wires of the same material and diameter are suspended in pairs about an inch apart from each other, and are attached by one extremity of each to the same support; the other extremities being fastened in the one case to a scale-pan, and in the other to the centre of a bar of wood or metal carrying constant equal weights at each end: the latter wire is provided with a scale and the former with an index of some sort, which being level with and close to the scale, serves to measure any alteration of length produced by weights placed in the pan.