That said courts (circuit courts of the United States), when sitting in equity for the trial of patent causes, may impanel a jury of not less than five and not more than twelve persons, subject to such general rules iii the premises as may, from time to time, be made by the Supreme Court, and submit to the court such questions of fact arising in such cause as such circuit court shall deem expedient; and the verdict of such jury shall be treated and proceeded upon in the same manner and with the same effect as in the case of issues sent from chancery to a court of law and returned with such findings.