Science: Weather Once a Week

Meteorologists have never been able to pin down a regular pattern in the weather, beyond the daily and annual cycles. But in late 1949, Rainmaker Irving Langmuir started releasing silver iodide particles in the skies over New Mexico on the same day each week. His idea was to see if this "weekliness" showed up in weather statistics gathered all over the country. According to a report in last week's Chemical and Engineering News, Langmuir is sure that it did.

In the Mississippi and Ohio Valleys especially, he found that the rains fell in a strongly marked seven-day cycle. Variations in barometric pressure, humidity, temperature, etc., followed the same weekly schedule. Langmuir does not maintain that his silver iodide went all the way to Ohio. But he thinks that New Mexico is a "weather breeder" where weather developments begin and sweep off toward the east. In the past, these weather changes came at irregular intervals. During 1950 they were triggered once a week by silver iodide and so, says Langmuir, brought weekly rain to faraway Ohio.