All mining claims upon veins or lodes of quartz or other rock in place, bearing gold, silver or other valuable mineral deposits heretofore located, shall be governed as to length along the vein or lode by the customs, regulations and laws in force at the date of such location.

For earlier acts on this subject, see: 1867 pp 146-147, 1869 pp 386-388, 1873 pp 444-446, 1875 pp 126-127, 1877 pp 335-336. See also, act of congress, May 10, 1872.