Bruun (P) leased a lot of land and the building thereon for 99 years on July 1, 1915. The lease provided that the lessee could tear down any building on the land. In 1929, the tenant demolished the building and constructed a new one with a useful life of 50 years. On July 1, 1933, the lease was canceled for default in payment and P regained possession. It was stipulated that the building had a fair market value of $64,245.68 and the value of the removed building was $12,811.43 for a net gain of $51,434.25. The Commissioner (D) determined that P realized that sum as a gain. The Tax Board overruled that determination, and the Circuit Court affirmed.