III. On some recent researches in solar physics, and a law regu­lating the time of duration of the sun-spot period

Abstract

1. In the short account of some recent investigations by Professor Wolf and M. Fritz on sun-spot phenomena, which has been published lately in the ‘Proceedings of the Royal Society' (1871, vol. xix. p. 392), it was pointed out that some of Wolf’s conclusions were not quite borne out by the results which we have given in our last paper on Solar Physics in the Philosophical Transactions for 1870, pp. 389-496. A closer inquiry into the cause of this discrepancy has led us to what appears a definite law, connecting numerically the two branches of the periodic sun-spot curve, viz. the time during which there is a regular diminution of spot-produc­tion, and the time during which there is a constant increase. It will be well, for the sake of clearness, to allude here again, as briefly as possible, to Professor Wolf’s results before stating those at which we have arrived.