case Lyddall v weston January the that the court of chancery in carry  agreement into execution govern themselves by a moral not a mathematical  certainty where the crown have only a bare reservation of royal i they can  grant a licence to any person to come upon another man estate and search for  such i but when i be once open they can restrain the owner of the soil from  work they and can either work the i themselves or grant a licence for other to  work they there be a reservation in a grant of a estate by the crown of tin  lead and all royal i within the premise the master statesit there be a  probability that there be such i and therefore lie report the plaintiff Mr  lyddal can make a good title atkins the exception be that the master be  mistake for there be no evidence of such i or even a probability of they Lord  chancellor I be of opinion the exception be well find this be one of the case  of willingness and unwillingness in a purchaser it be the business of this  court to carry such agreement into execution and must govern itself by a moral  certainty for it be impossible in the nature of thing there shall be a  mathematical certainty of a good title No pretence that there have be any  search for royal i for year and upon examination the probability be great that  there be no such i there be often suggestion of old entail and often doubt  what issue person have leave whether more or few and yet these be never allow  to be objection of that force as to overturn a title to a estate No instance  where the crown have only a bare reservation of royal i without any right of  entry that it can grant a licence to any person to come upon another man  estate and dig up his soil and search for such i I be of opinion there be no  such power in the crown and likewise that by the royal prerogative of i they  have even no such power for it will be very prejudicial if the crown can enter  into a subject land or grant a licence to work the i but when they be once  open they can restrain the owner of the soil from work they and car either  work they themselves or grant a licence for other to work they it will be of  mischievous consequence to allow it to be a objection to a title that it be  derive under a grant from the crown in which there be a reservation of such i  especial as all grant from the crown have for the most part such a general  reservation but the fact in the present case be there have never be a exertion  of this right in a single instance since the grant and no probability there  ever will Reg lib b fol atkins er p