1 "'art I. Elementary correlation, and "accidental deviations." 2 1. Requirements of a good method. 2 2. Standard methods explained. 6 3. Comparison "by rank. 8 4. Auxiliary methods. 11 Part II. Correction of "systematic deviations." 17 1. Systematic deviations generally. 17 2. "Attenuation" "by errors. 18 3. Limits of associative problems. 21 4. "Constriction* and "Dilation. " 23 &. "Distortion." 24 6. Critioism of prevalent working methods.25 1. "General Intelligence" determined and measured, to appear in a subsequent number of this Journal.m 3.1. "Proceedings Royal Society of London", Vols XL and XLV.2. Commonly, but misleadingly, termed the 'probable error."'tiaXa'jao'o-

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In the history of psychology this famous paper marks an important milestone as the original work from which factor analysis was to develop. It provoked a storm of controversy from the experimentalists on the one hand and the measurement researchers on the other; it set the stage for the long debate which was to follow over "general" versus "specific" tra'rts.

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By C. SPEARMAN. 1. 2. Proposed general procedure. 3. Il'irst method of measuring the average limen. 4. TJbe case of equal intervals. 5. Second and slightly more accurate method of naeasuring the 6. Mean deuiation. 7. Conclusion. Need of dispensing u i t h the Gaussian formulae in ti@ method of 'right and wrong cases.' average lirnen.