Swans hatched during Thunder

Some years ago I purchased a pair of swans, and, during the first breeding season after I procured them, they made a nest in which they deposited seven eggs. After they had been sitting about six weeks, I observed to my servant, who had charge of them and the other water-fowl, that it was about the time for the swans to hatch. He immediately said, that it was no use expecting it till there had been a rattling peal of thunder to crack the egg-shells, as they were so hard and thick that it was impossible for the cygnets to break them without some such assistance. Perhaps this is the reason why s…