18 Mr. F. Gal ton. Remits derived from the Natality [Jan. 18, 



III. "Results derived from the Natality Table of Koroei by 

 employing the Method of Contours or Isogens." By 

 FRANCIS GALTON, F.R.S. Received January 12, 1894. 



There are three variables in the statistics of natality. The age of 

 the father is one, that of the mother is another, and the percental 

 offspring of parents of those ages is the third. These three variables 

 may be coordinated in the same way as that which is daily followed 

 at meteorological offices in dealing with (1) the longitudes of the 

 various stations, (2) their latitudes, and (3) the barometric height 

 at each. After these data have been entered on a chart in their 

 proper places, contours, known by jthe name of isobars, are drawn to 

 show the lines of equal barometric pressure. In natality tables, the 

 ages of the father and the mother take the place of the longitudes 

 and latitudes in weather charts, aud lines of similar birth rates, or 

 as I would call them, " isogens," take the place of isobars. 



Table I contains the means of each set of four adjacent entries as 

 shown by the arrangement below, the left-hand diagram showing 

 the four entries, and the right-hand one showing their mean. The 



Father's Age. 

 38 39 



40 



39 



28 



|29 



30 



21 



21 



23 



32 



24-25 



29 



entries themselves were copied to the nearest integer from Korosi's 

 tables. The means are recorded in Table I to the nearest integer only, 

 subject to an allowance of correction not exceeding 0'30 for the sake 

 of slight smoothing ; thus 24'25, which would otherwise have been 

 entered as 24, might be treated as if it were 24'25-f 0'30 = 24'55 and 

 be entered as 25. Similarly 24'75 might be entered either as 25 or 

 as 24. It will be seen by the right-hand diagram that the position of 

 the mean corresponds to the first moment of the years shown at 

 the side and top; therefore the interval to which the annual birth 

 rate corresponds is made up of the half year before and after that 

 epoch. 



The means that are enclosed in brackets are those in which one or 



