I disagree with Dr. Pode's final punch-line, "In the best schools three chemistry courses should be available: CBA, CHEM Study, and an Advanced Placement course to cater to those who have been fired with enthusiasm by either of the others." It is not important that a school offer CHEM Study or CBA or even an advanced placement course. The definitive course has yet to be written; the specific track we take is not important. Also, in the light of our new courses in chemistry, we should take a fresh look a t Advanced Placement. Whether such work is still needed and whether the high schook are offering the equivalent of a first year college course (what is it?) are moot questions.
To the Editor: Mr. Saul Geffner's remarks about the Teacher's Guides illustrate rather clearly the competitive spirit in which the relative merits of CBA and CHEhl Study tend to be approached in the USA-which I deliberately tried to play down in my article. Naturally enough the CBA guide has references to further reading, whereas the CHEM Study guide helps with some specific classroom queries; hut I doubt that an impartial reader will disagree with my statement that the stress in the CBA T.G. is on helping with specific classroom situations, whereas the stress in the CHEMS T.G. is laid on giving the teacher a sense of the structure of chemistry at a more advanced level than the student could understand. Both these aims are valuable, but they are different. To the outsider it is the extraordinary divergence between CBA and CHEMS in the means they adopt to produce the same result-the enthusiastic freshman chemistthat is so startling. My punch line--like most punch lines-can be misinterpreted. By dwelling on the differences b e tween CBA and CHElLlS and then saying that every school should have both, I was pleading for variety, not uniformity. I am sure that Mr. Geffner does not believe that by labeling a chemistry course as CHEM Study, that course is necessarily closely defined. Courses with that label as taught in the private schools in the northeast are considerably different from those in San Antonio or in San Francisco. The function of curriculum experiments is to provide materials for the teacher to use; no two classes are identical, and the teacher-if he is more than just a public address system-will produce his own highly personal approach to either course.
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Finally, on the subject of Advanced Placement, I agree entirely that an attempt to duplicate some of the highly original first year teaching which is emerging in many colleges in the USA, without the advantages of highly qualified staff and expensive equipment, is asking for trouble. Oxford and Cambridge have suffered in the past from schoolmasters "skimming the cream" from the first and second year university work, with the result that such topics contain no e l e ment of intellectual surprise or excitement for the undergraduate. I believe that a year spent in applying the theoretical concepts already covered to further e l e ments and periodic groups, extending the organic chemistry to a deeper understanding of functional groups supported by laboratory work, relating theoretical chemistry to the study of raw materials and industrial processes, and finally attempting a small-scale project to learn how difficult research is, gives a prospective freshman valuable experience without blunting his appetite.
To the Editor: I n an article discussing molecular symmetry and point groups [M. ZELDIN,Tms JOURNAL, 43, 17 (1966)], the author makes the statement that the Schoenflies system is "restricted to point group symmetry" while the Hermann-Mauguin system is "applicable to both point and space group symmetries." While the s t a t e ment is technically correct, it seems that it could have been worded a little more clearly. As it stands, it leaves the false impression that the Schoenflies system cannot he used to designate space groups. The Schoenflies system has indeed been used to designate space groups, but it does so in terms of the point groups from which they are derived without indicating other symmetry elements which may have been introduced. I t is this limitation that led to the development and adoption of the Hermann-Mauguin notation. The Hermann-Mauguin notation indicates all the symmetry elements present in a point or space group while at the same time labeling it. Use of this system does not require one to study complicated charts such as Figure 7 in the article referred to. This symbolism was first introduced by C. Hermann [Z. Krist. (A) 68, 257 (1928)l and later simplified by Ch. Mauguin [Z. Krist. (A) 76, 542 (1931)l.
