[B] In this and the next two Tables the intensity of the illumination of the D ray before reduction is equal to that of an amyl-acetate lamp at one foot from a screen. The figures in Col. VII. are in millionths of the illumination of an amyl-acetate lamp at one foot distant, every ray being made of that intensity. TABLE IX.--H. R.’S CURVES (see Fig. 32). -------+--------+------------+------------+-------------+-----------+------------ I. | II. | III. | IV. | V. | VI. | VII. -------+--------+------------+------------+-------------+-----------+------------ Scale | Wave- | Mean | Adopted | Persistency | Luminosity| Absolute number.| length.| reading of | reading in | curve | curve. | luminosity | | extinction | millionths | (590 / | | of | | in | of |ad. reading).| | extinction | | millionths | original | | | (IV.×VI.) / | | of | luminosity.| | | 48 | | original | | | | | | luminosity.| | | | -------+--------+------------+------------+-------------+-----------+------------ 57 | 6423 | 1200 | 1200 | ·49 | 5 | 125 56 | 6330 | 900 | 850 | ·69 | 7 | 124 55 | 6242 | 500 | 550 | 1·07 | 10 | 115 54 | 6152 | 250 | 250 | 2·36 | 17 | 88 53 | 6074 | .. | 150 | 3·93 | 25 | 78 52 | 5996 | 90 | 90 | 6·56 | 35 | 66 51 | 5919 | 60 | 45 | 13·1 | 47 | 44 50 | 5850 | 27 | 27 | 21·8 | 57 | 32 48 | 5720 | 18 | 15 | 39·3 | 66 | 21 46 | 5596 | 10 | 10 | 59 | 69 | 14 44 | 5481 | 9·3 | 8 | 73·8 | 64 | 11 42 | 5373 | 6·5 | 6·2 | 95·1 | 56·5 | 7 40 | 5270 | 5·9 | 5·9 | 100 | 45 | 5·5 38 | 5172 | 6 | 6 | 98·3 | 32 | 4 36 | 5085 | .. | 6·6 | 89·4 | 20 | 2·7 35 | 5043 | 7 | 7·2 | 81·9 | 16 | 2·4 34 | 5002 | .. | 8 | 73·8 | 12·5 | 2·1 32 | 4924 | 10 | 9·6 | 61·5 | 8 | 1·6 30 | 4848 | 11·5 | 12 | 49·2 | 6 | 1·5 28 | 4776 | 14·5 | 14·5 | 40·7 | 5 | 1·5