Personal Equation in the Tabulation of Thermograms, &c

Abstract

MR. PLUMMER, in his letter (NATURE, vol. xii. p. 395), has missed the point of the review of the work of the Meteorological Office referring to the tabulation of temperatures (vol. xii. p. 101). From 1,283 estimations of tenths of seconds, as tabulated by the highly-trained and experienced observers at Greenwich, he shows that the whole seconds estimated were 15 per cent. of the whole number, and thereupon remarks that this is precisely the excess of whole seconds that is taken in the review of the work of the Meteorological Office as indisputably proving the carelessness of the tabulations at the Kew Observatory. This is a mistake. Kew was not singled out for criticism because the whole degrees tabulated there amounted to 15 per cent. of the whole number, but because of “the irregularity of the tabulations, more especially as regards the tabulations from day to day.” An examination of the tabulations at Kew from day to day shows that there are first-class tabulators in that Observatory, but it also shows there are others whose work is inferior. Thus, in the first published sheet for Kew, viz., January 1874, on seventeen of the days the whole degrees tabulated amounted on each of these days to at least 25 per cent., and the average of the whole seventeen days reached 31 per cent., or nearly a third of the whole. On the remaining fourteen days of the month the average was 14 per cent. Hence the variations of the numbers of whole degrees from month to month, which, as stated in the review, were 172 for January, 87 for February, 127 for March, and 94 for April. It is this irregularity in the work of tabulation which has lowered the character of the work done at Kew.