ON THE MOTION OF PENDULUMS. 91 of any of the experiments, or the detection of any numerical error which I may have committed. I may here observe that I have not, generally speaking, re-examined the calculations, except where an error was apparent, but that each step requiring addition, subtraction, multiplication, or division, was checked immediately after it was performed. I have not thought it requisite to check in this manner the taking of logarithms or antilogarithms out of a table. Values of T, k, and ki employed in the calculation of the theoretical results employed in the two preceding tables. (For the description of the pendulums Nos. 45 to 53, see p. 89.) Long rods Short rods No. T k *i No. T k h. 45 1-090 0-7968 1-951 46 1-158 0-7170 1-981 47 1-227 0-6523 2-010 48 1-155 0-8055 3-222 60 0-9517 0-7772 3-012 49 1-198 0-7207 3-264 61 0-9806 0-7005 3-042 50 1-222 0-6520 3-288 62 0-9982 0-6373 3-062 51 1-190 0-8099 7-272 63 0-9868 0-7824 6-649 52 1-199 0-7208 7-299 64 0-9954 0-7021 6-679 53 1-231 0-6525 7-396 65 1-0030 0-6377 6-714 The corrections for confined space employed are, for the spheres, (A/c), O'Ollo, 0'0321, 01013; and for the rods, (AAJ, 0-009, 0-002, 0*000. These corrections are to be added to the values of k, k^ given in the preceding table before going on with the calculation. 61. In the 14th set of experiments, the weight of adhesive air due to the spheres alone has been computed by Baily by subtracting from the whole weight, as given by observation, the weight due to the rods as given by the 13th set of experiments, taking account of the change of weight corresponding to the change in the position of the centre of gyration, the point at which the air is supposed to be attached. According to theory, this process is not legitimate, inasmuch as the weight dragged by a rod is a function of the time of vibration, which is altered when a sphere is attached to the end of the rod. But in the 15th set