TY - JOUR T1 - Addendum to Description of Photometer JF - Proceedings of the Royal Society of London (1854-1905) VL - 17 SP - 369 EP - 370 PY - 1868/01/01/ UR - http://dx.doi.org/10.1098/rspl.1868.0070 M3 - doi:10.1098/rspl.1868.0070 AU - Crookes, W. ER -