The more comprehensive data for the study of the stellar temperature scale are the spectrophotometric measures of Wilsing and Scheiner,[47] of Wilsing,[48] of E. S. King,[49] and of Rosenberg.[50] The temperature scales derived by Wilsing and by Rosenberg differ by a linear factor; Rosenberg assigns higher temperatures to the hotter stars, and lower temperatures to the cooler stars. These temperature scales, and their intercomparison, have been very fully discussed by Brill,[51] who reduces all the measures to the scale given by Wilsing, and gives, for the principal Draper classes, the following comparative table for the corrected mean effective temperatures on the absolute centigrade scale. In addition to the comprehensive data just quoted, there have been [Pg 30] numerous determinations of the temperatures of individual bright stars, chiefly by Abbot,[52] Coblentz,[53] Sampson,[54] and H. H. Plaskett.[55] In the main these values confirm the scale given in Table V, but sometimes considerable differences occur in the values given for individual stars by different investigators. At the same time, each observer is usually reasonably self-consistent, and the deviations must therefore be ascribed to differences of method. Some of the results are reproduced, for illustration, in Table VI. TABLE V Class Wilsing Rosenberg E.S. King Color Temperature E.S. King Total Radiation 12300° 30000° 22700° 22700° 11450 18000 15200 14900 10250 1200 11600 11300 9000 9000 8800 8600 7950 7850 7900 7700 6880 6930 7000 6800 5980 6000 6040 5870 5250 5200 5090 4950 4570 4570 4570 4440 3860 3840 3640 3550 3550 3580 3430 3340 It is seen that the effective temperatures of individual hotter stars vary widely among themselves. This is largely a result of the difficulty of making the appropriate correction for atmospheric extinction. It must, then, be supposed that the temperatures derived by spectrophotometric methods are not trustworthy for stars hotter than Class . The values determined by the earlier observers for the and classes are almost certainly too low. Rosenberg’s value of 30,000° for is, however, most probably too high, as will be inferred later from the ionization temperature scale. For the cooler stars small discrepancies also occur among the different observers. In the writer’s opinion, the lowest estimates for the [Pg 31] temperatures of the cooler stars are probably nearest to the truth. TABLE VI Star Abott Radiometric Coblentz Thermoelectric Plaskett Wedge Method Sampson Photoelectric Ori() 13000° 25000° Cas() 15000° 30000 Per() 15000 14000 Ori() 16000° 10000 14800 Lyr() 14000 8000 11600 () 11000 12800 ( Cyg() 9000 9000 10900 Aql() 8000 Cas() 9000 10700 () 6000 8300 Aur() 5800 6000 5500-6000 5500 * () 4000 4200 Gem() 5500 5000-5500 4200 Tau() 3000 3500 3400 Ori() 2600 3000 3400 Peg() 2850 3200