----------------------------------------------------------------------- ---------------------------------+-------------+-----------+----------- | Deflection | Light | Source of Light. | in | in | E. M. F. | Millimetres | Candles. | Volts. ---------------------------------+-------------+-----------+----------- 1896 Candle at 10 feet distance | 18.70 | | Betelgeuse (0.9 mag.) | 12.80 | 0.685 | 0.026 Aldebaran (1.1 mag.) | 5.21 | 0.279 | 0.012 Procyon (0.5 mag) | 4.89 | 0.261 | 0.011 Alpha Cygni (1.3 mag.) | 4.90 | 0.262 | 0.011 Polaris (2.1 mag.) | 3.10 | 0.166 | 0.007 ---------------------------------+-------------+-----------+----------- 1 volt. | 432.00 | | | | | 1895 Arcturus (0.3 mag.) | 8.2 | 1.01 | 0.019 Vega (0.1 mag) | 11.5 | 1.42 | 0.026 Candle at 10 feet | 8.1 | | ---------------------------------+-------------+-----------+----------- N.B.--The standard candle shone directly on the cell, whereas the star's light was concentrated by a 2-foot mirror. The sensitive surface on which the light of the stars was concentrated was 1/20 inch in diameter. We must therefore diminish the amount of candle light in this table in the proportion of the square of the diameter of the mirror (in 1/20 of an inch) to one, equal to 1/230400. If we make the necessary reduction in the case of Vega, and also equalise the distance at which the candle was placed, we find the following result:-- Observer. Star. Candle power at 10 ft. Minchin. Vega 1/162250 Nichols. " 1/22000000 This enormous difference in the result is no doubt largely due to the fact that Mr. Nichols's apparatus measured heat alone, whereas Mr. Minchin's cell measured almost all the rays. And this is further shown by the fact that, whereas Mr. Nichols found Arcturus a red star, hotter than Vega a white one, Mr. Minchin, measuring also the light-giving and some of the chemical rays, found Vega considerably more energetic than Arcturus. These comparisons also suggest that other modes of measurement might give yet higher results, but it will no doubt be urged that such minute effects must necessarily be quite inoperative upon the organic world.