VOL.8, NO. 3
EXORCISING A SPECTRE: ENTROPY
503
with its proper numerical value of entropy (calculated from any convenient "line of zero entropy") in imitation of the usual diagram of labeled isothermals, and this may be followed by the introduction of the S-Tdiagram, which, important in itself and usually entirely overlooked in a short course, automatically raises S from obscurity to the rank of a definite quantity capable of taking on definite numerical values. The process of plotting a system of isobars in the S-T diagram is a very great aid in makin2 entropy a familiar and usable tool. This method of introduction, somewhat modified. is being used in teaching the course in thermodynamics offered to c ndidates for the master's degree in chemistry. It is found that, even after the preliminary treatment of thermodynamics received as undergraduates in courses on heat engines or physical chemistry, the student is likely to have only the vaguest notion of what entropy is or stands for and is prone to use formulas without attempting to master their full content and significance. The method outlined here is offered in the hope that it may be of use elsewhere. Literature Cited ( 1 ) GEIGERand IX, p. 51.
SCHBEL, "Handbuch der Physik," Julius Springer Berlin. 1926, vol.
Ultra-Violet Shows Up the Check Raiser. The treatmrnr of check paper with aesculin, a white powder obtained from the bark of the horsechestnut tree, makes it possible for the bank teller to detect with ease erasures and changes which otherwise might escape notice. Aesculin fluoresces, or glows, when placed under ultra-violet light. An erasure an paper treated with this substance would show up as a dark spot on an otherwise luminous surface. A patent on the process has recently been granted to Dr. D. Julian Block. -Science Sewice Good Students Found to Be Rapid Readers. The college student who doesn't know how to study may now be told to have his eye-motions photographed. For these eye photographs may show that he glances hack frequently, instead of fixing his eye effectively on each new group of words. The photographs may show that he reads very slowly and pauses many times as his eye moves across the page. That inefficient reading habits, such as these, link with weak study habits is found by two psychologists. Dr. W. R. Miles and H. M. Bell, who have photographed the eye movements of university students as they read a difficult passage on "didactic poetry." The students' speed in completing the paragraph was compared with their scholastic ability. The most rapid readers sped along about twice as fast as the slowest, it was found. These fast readers as a rule showed the most extensive spans of print taken in by the eye a t one fixation before i t moves to take in the next group of words. The fast readers looked back fewer times to correct inaccuracies in their fixation. Readers look back most frequently a t the middle or right end of a line of print, the experiments indicate.-Science Service
