Sections 1.611-1 through 1.614-8, inclusive, are prescribed under the authority granted the Secretary or his delegate by section 611(a) of the Code to prescribe regulations under which a reasonable allowance for depletion and depreciation of improvements shall be allowed, according to the peculiar conditions in each case, in the case of mines, oil and gas wells, other natural deposits and timber. [T.D. 6965, 33 FR 10692, July 26, 1968]