In Single Residence and General Residence Districts no land shall be used for any purpose for which a new building or structure may not be constructed or used under the provisions of this Bylaw; in said districts the removal of sod, loam, sand, gravel or quarried stone for sale, except when incidental to and in connection with the construction of a building for which a permit has been issued in accordance with the Building Laws, shall be permitted only if permission of the Board of Appeals be obtained in accordance with the procedure provided in Article 45, and only under such conditions as they may impose; but nothing contained in this section shall prevent the continued use of any land for the purpose for which it is used at the time this section takes effect, nor prevent the use of any land for farms, gardens, nurseries, cemeteries, parks, playgrounds and such purposes as are incidental to or usual in connection with any of said purposes.
