--------+---------+---------------+------------+---------------- Scale | Wave- | Mean reading | Luminosity | Luminosity of Number. | Length. | of the colour | of the | the rays when | | limit of the | ordinary | each colour | | spectrum D, | spectrum. | disappears, | | being 1 amyl | | each ray having | | lamp in | | the original | | 1/10000ths. | | luminosity of | | | | 1 amyl lamp | | | | in 1/100000ths. --------+---------+---------------+------------+---------------- 61 | 6839 | 120 | 4 | 48·0 60 | 6728 | 67 | 7 | 46·9 58 | 6520 | 26 | 21 | 54·6 56 | 6330 | 13 | 50 | 65·0 54 | 6152 | 9·5 | 80 | 76·0 52 | 5996 | 9·0 | 96 | 86·4 50 | 5850 | 9·0 | 100 | 90·0 48 | 5720 | 9·0 | 97 | 87·3 44 | 5481 | 9·5 | 75 | 71·3 40 | 5270 | 10·5 | 50 | 52·5 36 | 5085 | 12·5 | 24 | 30·0 32 | 4924 | 18 | 8·5 | 15·3 28 | 4776 | 32 | 4·0 | 12·8 24 | 4639 | 55 | 1·8 | 12·0 20 | 4517 | 90 | 1·08 | 9·7 16 | 4404 | 160 | ·70 | 11·2 12 | 4296 | 250 | ·45 | 11·0 8 | 4197 | 400 | ·26 | 10·4 4 | 4106 | 700 | ·14 | 9·8 --------+---------+---------------+------------+---------------- TABLE VI.--EXTINCTION BY CENTRAL PORTION OF NORMAL EYE (see Fig. 28).