Details of Experiments. The first experiments were made in 1873, March 28, and they were continued regularly until April 16. The rod of fiintglass was suspended in air, water, and oil. A rotation was nearly always communicated to the rod when contact was made with the electro-magnet. When the magnetism of the electro-magnet was reversed I sometimes got a rotation in the opposite direction, and sometimes a rotation in the same direction, but to a different extent. The apparatus was repeatedly dismounted and set up again with all the parts changed. The effects were generally unaltered. In noting the experiments, I used the terms "no contact," "right contact," and "left contact," as being least liable to lead to error. "No contact means that the circuit was broken. "Right contact" means that the lower pole of the electro-magnet would, if free, point to the north. "Left contact" means that the lower pole of the magnet would, if free, point to the south. When the readings of the scale are increasing the glass is rotating in the direction of the hands of a watch with the face upwards. The glass was sometimes put into water or oil, and in this case also rotation was generally observed. The rotation oscillations in air were so great as to necessitate reading the scale at the end of each half oscillation, and taking a mean. In the following table each reading is a mean of many observations: Flint-Glass in Oil. Right and left contact each continued to diminish the scale reading during twenty-two minutes. The change from left to right contact diminished the readings with a jump. "No contact" again reversed the rotation. The poles of the electro-magnet were now put so far to the east of the glass as possible, and again as far to the west. kind of results were obtained. The same Oil was again used, and no certain effect was observed. March 31.-The apparatus, as left last day, with oil in the jar, showed no effect. No effect was shown with air. But on trying a new rod of flint-glass the old effects were observed. destroyed the effect. Flint-Glass in Air. The oil seemed to have Right contact, steady rise from 400 to 543 in about 4 minutes. By keeping right contact for decreasing rotation-swing, and left for increasing, the range of swing increased after 6 swings to 123 divisions. On reversing this action for 6 swings the range was reduced to 12 divisions. Note. These are the most striking experiments. It will be noted that here the "right" gives lower readings than the "left" contact. But I cannot be sure that the commutator arrangements had not been changed. Here all disturbing effects are done away with, and the right and left contacts produce deflections on opposite sides of the "No contact" reading. A new rod was now prepared, which also showed a very decided difference between right and left contact, right being lowest. Numerous experiments under various conditions were now tried, but no new effects were discovered. It is desirable, however, to record the following, which were made to be certain as to the direction of rotation under different conditions of polarity : No contact, Upper pole would point to north if free, 850 840 848 854 835 850 845 The general result of the experiments of the winter is, that when a pole tending to point to the north is above the glass rod, and a pole tending to point to the south is below, the rod turns in the opposite direction to the hands of a watch with the face upwards. On placing the magnet with the poles in a horizontal plane, rotations were sometimes observed. This is in direct contradiction to the theory that led to these experiments. I can offer no explanation, but merely record the fact. In the session 1873-74 similar experiments were made with a |