Abstract
Summary: The seasonal distribution of the sex ratio of livebirths has already been correlated with the seasonal distribution of rainfall approximately 320 days earlier. The daily rainfall readings and the daily analysis of drinking water in Brisbane, Queensland, have now been compared with daily births in the maternity hospitals of that city. The interval between the two sets of events ceases to be a mere approximation and becomes a fairly precise 320 days.There was also an interval of exactly 320 days between the smog which covered Greater London from 5th to 9th December 1952, and the births of 109 males and 144 females at 16 London hospitals from 22nd to 26th October 1953. That anomaly occurred in the middle of an extended period during which very masculine sex ratios had otherwise consistently prevailed.