case clavering versus clavering see Elias v snowdon slate Quarries   App Cas  Lord chancellor king Sel can in Charles mose Eq can ab pl tenant for life of  coal i may open new pit or shaft for the work the old vein of coal the  defendant be tenant for life of land in Durham but not without impeachment of  waste the plaintiff be the remainderman in tail and in these land there be  several i of coal which be open before the defendant the tenant for life come  to the estate and the tenant for life open the earth in several place but as  it be say with design only to pursue the old vein of coal and the plaintiff  move for a injunction to stay the defendant from open the earth in any new  place Lord chancellor this be determine in the great cause of hillier v  Twiford in which I be of counsel the matter be peer William try at the assize  in Devonshire before Mr justice Powel and hold great part of the day there it  be prove by witness to be the course of the country and a practice well know  in those part among the miner that any person have a right to dig in i may  pursue the I and open new shaft or pit to follow the same vein and that  otherwise the work in the same i will be impracticable because the miner will  be choke for want of air if new hole shall not be continual open to let the  air in to they and the same vein of coal frequent run a great way and as Lord  chancellor express it the same I of coal be very knowable and easy to be  discern beside that to stop the work may be the ruin of the colliery for ever  and in the present case it appear that there be a fire engine keep by the  tenant for life of these i which carry off the water without which the i will  be lose and the work of this fireengine cost pound or pound a week then it be  object by the attorney general that these i be not open when the settlement be  make have be open by the person who by that settlement claim a estatetail and  be since dead without issue whereas the settlement give only the benefit of  the i then open to the tenant for life peer William er p say per cur it seem  as if the tenant for life may work all i which be lawful open by the precedent  tenant in tall though subsequent to the settlement so deny the injunction