 This was a result of the "rail nurse", a shot in which the object balls are nudged at very soft speed down a rail to a duplicate position again and again.The solution was to require that all shots include contact with at least one cushion before the second object ball is contacted, an idea taken from an early form of English billiards called the "doublet game".Later, between 1881 and 1889, a new nurse shot was developed for one-cushion, known as the "rub nurse".