16. When there is a question whether a particular act was done, the existence of any course of business, according to which it naturally would have been done, is a relevant fact.

Illustrations

(a) The question is, whether a particular letter was dispatched.

The facts that it was the ordinary course of business for all letters put in a certain place to be carried to the post, and that that particular letter was put in that place are relevant.

(b) The question is, whether particular letter reached A.

The facts that it was posted in due course, and was not returned through the Dead Letter office, are relevant.