WHEN, as will occasionally happen, unexpected "regrets" require thirteen at table, the host and hostess may find it well to fortify themselves with the following incident:
A hostess at a party in London once had arranged a party of fourteen to dine with her, sayeth deponent.
At the last moment the late Lord Kelvin had to send his excuses. The superstitious hostess was unable to find a desirable person to fill the gap, and wrote to the scientist explaining her predicament, and entreating him to come.
Lord Kelvin still replied that it would be impossible. He pointed out, however, that her superstition was illogical on the following grounds :
If the average age of the company proved to be 72½ years -a ridiculous supposition there would exist a scientific probability that one of them would die within a year.
If the average proved less than this, there would be no probability whatever.
If the average age proved 20 years, there would have to be 129 persons at table before there would be any scientific probability of one of them dying within a year.
If 30, there must be 119; if 40, 103; if 50, 73; if 60, 35 ; and if 70 years, 17.
