A. O. POWYS 
31 
TABLE I. 
Births per 100 Wives in Arje Groiqjs. Experience of New South Wales. 
Mean Annual Numbers for six years 1893-8. 
Age Group 
Mean Annual 
Marriages 
Ante-nuptial 
Conceptions 
Unprejudiced 
Marriages 
Mean Annual Births 
from 9 to 12 months 
after Marriage 
Births per cent, 
of unprejudiced 
Marriages 
Under 20 
1400 
568 
832 
208 
25-0 
20 and under 25 
3719 
1150 
2569 
995 
38-7 
25 „ 30 
1869 
366 
1503 
596 
39-6 
30 „ 35 
622 
98 
524 
160 
30-5 
35 „ 40 
304 
35 
269 
43 
16-0 
40 „ 45 
133 
7-5 
125-5 
5-2 
4-1 
The fourth cokimn shows the difference between the second and third columns, 
leaving what we may term "unprejudiced" marriages. The fifth column shows 
the births following such unprejudiced marriages within the period 9 to 12 
months after marriage, whilst the sixth column gives the percentage ratios 
between columns four and five. On reference to the diagrams it will be seen that 
the range extends from 14'5 years to about 45"8 years, with the maximum at 
about 24'5 years. 
The actual curve determined by Mr Powys is 
;' = «'»n' + 2wr4) ('-J^o) • 
with the mean at 27"00 years and mode at 24'49 ; the unit of a- is five years. 
As the five year unit of grouping is rather large Dr Alice Lee again worked 
out the constants of the curve, using Mr W. F. Sheppard's corrections* for the 
moments. The curve was now found to be 
y = 41-504 (l+^-^-g) [l-^^^] , 
with the mean at 27"048 years, the mode at 23'707, and the range from 1.5-62 to 
44'27 years. It may be doubted whether this determination is as good as the 
previous one, for the curve rises vertically at the left-hand terminal of the range, 
and thus Mr W. F. Sheppard's corrections are shown by the resulting curve to be 
inapplicable to this case. 
Table II. gives the like results for a special tracing from the Register of 
Victoria of the births resulting from the marriages contracted during the year 
1897. On comparing the resulting curve with that for New South Wales it will 
be seen that the latter is higher in the earlier ages and lower in the later years 
than the former. 
* Lond. Math. Soc. Proc, Vol. xxix., p. 369. 
