Variable-extinction analyses for 51 galactic clusters, using primarily zero-age main-sequence-fitted data, are presented and discussed. For three of these clusters, spectroscopic data for the brighter stars are presented. The weighted mean value of R, the ratio of total to selective extinction, for all 51 clusters is 3.08 plus or minus 0.03, in very good agreement with the results of other determinations. Careful examination of the data for individual clusters suggests that some evidence for a dependence of R on intrinsic color and galactic longitude may be present.
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D. G. Turner (1976) studied this question.