TABLE II.—Showing the annual mean Rainfall of various parts of the World, from 1854 to 1872, compared with Wolf's relative numbers of Sun-spot. The comparisons are between the rainfalls at the same stations. The quantities in the column are derived from those in the column of Means by taking, for example, the mean of the falls in 1854 and 1856 and the mean of that mean and of the fall in 1855, and so on. First Report of the Committee, consisting of Dr. JOULE, Prof. Sir W. THOMSON, Prof. TAIT, Prof. BALFOUR STEWART, and Prof. MAXWell, appointed for the purpose of determining the Mechanical Equivalent of Heat. We are able to report that progress has been made with the experiments undertaken by Dr. Joule on behalf of the Committee. Friction of water is the method he has employed; and the average result of upwards of sixty experiments is 773-1 in British gravitation units at Manchester, the greatest deviation from the above average being * Experiments have yet to be made on the capacity for heat of the brass of which the calorimeter is constructed, which has provisionally been calculated from the results of Regnault for this alloy. The greatest possible error which may have arisen in this way is believed to be. Dr. Joule also proposes to compare his mercurial thermometers with the air-thermometer, with a view to obtain accurate boiling-points, and thus correct values of the thermometric scale. The greatest correction which it may be found needful to apply on this account amounts to about These maximum corrections, if taken in the same direction, would necessitate the addition of 4.5 to the equivalent above named. The experiments made by Hirn on the friction of water have led him to the number 786. But the average of his results, derived from the friction, boring, and crushing of metals, gives 774. Assuming that the above experiments and those made by Dr. Joule for the Committee on Standards of Electrical Resistance are to be relied on, the unit issued by it would appear to have a resistance too small by The Committee are happy in being able to state that Professor Maxwell has been working some time with a view to the redetermination of this unit, and that he has also undertaken fresh direct experiments for determining the dynamical equivalent of the thermal unit. Report of the Committee appointed for the purpose of promoting the extension, improvement, and harmonic analysis of Tidal Observations. Consisting of Sir WILLIAM THOMSON, LL.D., F.R.S., Prof. J. C. ADAMS, F.R.S., J. OLDHAM, WILLIAM PARKES, M.Inst.C.E., and Admiral RICHARDS, R.N., F.R.S. Draw up by Sir WILLIAM THOMSON. SINCE the publication in 1873 of the Committee's Report for 1872, a large amount of work has been gone through in the way of harmonic analysis, exhausting the funds at the disposal of the Committee for this purpose, but none of the results have hitherto been published. They are now offered for publication in this final Report of the Committee, and along with them, by permission *[These experiments, up to the present date, show a smaller capacity than that anticipated, bringing up the equivalent to 774-1, which will be subject to a small correction, possibly amounting to 5, on account of the thermometric scale error.-Note, November 13, 1876.-J. P. J.] |