Notwithstanding anything in section 71 of the Act of 1845, notice of all meetings of the Company (whether ordinary or extraordinary) may (if the directors so determine) be given by letter sent by ordinary post to each shareholder instead of by public advertisement:

Provided that the letters giving the notice shall be directed to the registered address or other known address of each shareholder and posted not later than seven clear days before the date of the meeting. In proving that any such notice has been given it shall be sufficient to prove that the letter containing the notice was properly addressed and posted by ordinary first class post as a prepaid letter not later than the time hereby prescribed.