How did jeans stay cool?

Link:
http://www.youtube.com/watch?v=6TRgokZLIwA


Photos:


Webistes:
http://en.wikipedia.org/wiki/Bell-bottoms
http://www.fiftiesweb.com/fashion/teen-clothing.htm
http://www.articleworld.org/index.php/Bell_bottoms
http://www.ehow.com/about_5381967_history-bellbottoms.html