Under the Act 1701, u. 6, a prisoner committed for trial may "run his letters," i. e. apply to the Court of Justiciary for an order that his trial shall be fixed within sixty days, after which it must be brought to a close within thirty days more, and in default of either condition, the prisoner may obtain his liberty. He cannot be again committed, except on express order of the Court ; and if not then tried within one hundred days, he is free from further proceedings.

Source: Kinnear, Digest of House of Lords cases (1865), pg. 361.