PACIFIC SOUTHWEST ASSOCIATION O F CHEMISTRY TEACHERS THE USE OF LANTERN SLIDES IN UNDERGRADUATE ORGANIC CHEMISTRY' NORMAN KHARASCR University of Southern California, Los Angeles 7, California
LECTURES in organic chemistry have a considerable tendency to become a twofold race against time. The instructor, with a prescribed amount of text in mind, busily engages himself in putting a wealth of detail on the blackboard; while the student, burdened by the pressure of examinations to follow, madly attempts to record it in his notes before the material presented is erased. The oft-repeated lament of the student, "He puts it on with one hand and erases it with the other," is not entirely fictitious. It is certainly true that by careful selection of material, by lucid and stimulating presentation, and by diligent preparation on the part of the student as well as of the instructor, the good teacher can and does largely avoid the above difficulty; and some, miraculously enough, can still find time within the lecture period to answer questions and to present some helpful demonstrations. But because of the extent of organic chemistry, and the need to develop the subject in sufficient detail to assure a realistic attitude to the work, the delivery of lectures in organic chemistry in a satisfactory manner is a challenging task which calls for the utmost of skill on the part of the instructor. In an attempt to increase the effectivenessof his own lectures to undergraduate classes in organic chemistry, the author has experimented for the past three years in presenting the material from lantern slides. The blackboard is used quite freely, but only as a secondary h e l p t o clarify now and again the discussion relating to the slides, and to give additional instruction as the needs of the moment may demand. The execution of this experiment has been quite enjoyable; and judging the response and performance of hundreds of &dents during several terms, the method seems to commend itself for serious consideration. On occasions when this development has been discussed with colleagues, there appeared $0 be good agreement on the point that slides could be very effectivefor 1 Summary of a lecture presented before Sympoaia arranged by the Pacific Southwest Aseociatian of Chemistry Teachers, San Francisco, Nov. 4,1949, and Los Angeles, Nov. 4,1950.
lecture instruction; but contradicting this, and equally dehite, was the feeling that there are certain difficulties which militate against the general use of slides in the classroom. Let us enumerate some of these objections and comment upon them in view of our own experience. A most frequent observation is that the preparation of slides is time-consuming, expensive, and accompanied by a bothersome storage problem. Furthermore, that once prepared, the slides will be used without revision for years, leading to a continually less effective course from term to term. In our experience, none of these factors need be serious. The majority of the slides used are made on the commercially available "Radio-Mats." Exclusive of glass covers, which may be used repeatedly as slides are revised (retail price about eight cents a set), the cost of mak'mg a suitable cellophane mat slide is only two or three cents per mat. As to the time required to make such a slide, it can be done as quickly as one wishes to write, draw, or type the material onto the mat. Thus, a very adequate set of cellophane mat slides, which may be kept for years or revised a t will, can be made a t low cost and with little or no more effort than is required to prepare a set of hand-written notes.l Although the acquisition of some black and white, as well as some colored, slides is advisable, i t is true that the cost of the photographic slides is higher, especially if they are sent out for processing. However, the photographic slides are likely to be suitable for longer continued use; and some of these can, if desired, be effectivelv - -ureuared in one's own laboratory a t moderate
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writing or on the Radio-mats, a helpful techniqueis to clip a square of the waxed paper and one of cellophane onto a glass plate, and to write directly onto the cellophane mat with a fine hall-point stylus. Dr. Karol J. Mysels has suggested an effective way of making slides quickly on frosted cellulosr-acetate film of suitable (0,0075 in.). The may be inserted between waxed and typed; or written onto with a colored or soft black pencil. The technique ie especially useful for tracing small drawings or charts from books or journals directly onto the transparent cellulose-acetate mat. Frosted glass plates m y , of course, also he used for the latter purpoae.
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cost. Hand-coloring of photographic slides is somewhat of a lost art, but makes a fascinating hobby for those who may choose to pursue it. As to revision of slides and the effect of this on the course: lethargy and lack of time may indeed result in failure to make the needed changes from term to term. But are these not the same factors which would retard the proper development of a course of lectures presented in any other fashion? And concerning the storage problem: we have found that convenient boxes for cataloguing and storing slides are available at relatively low cost. In the type of box aelected, the storage of 75 slides requires only 31/2in. of book-shelf space. A second point, often mentioned, concerns the need to darken the lecture room so that students are unable to take notes; and worse, "They go to sleep." A fairly modem projector with a thousand-watt bulb, used in conjunction with a "daylight" screen, gives sufficient brilliancy so that the image is perfectly clear, even in a large room with nearly normal daylight illumination. In some lecture halls, especially when showing photographic slides, it is desirable to reduce the illumination in the vicinity of the screen; but certainly there is no general problem in reserving ample illumination for taking notes. And with regard to keeping the audience awake: this is a problem which is not unique to lectures in which slides are used. In addition to the usual techniques which make for good audience contact, we have found that the well-timed projection of a cartoon slide or of a photographic slide of unusual interest allows for a brief diversion which proves quite effective. It has also been suggested that the instructor is freed of the labor required to put "all the stuff" on the board, and will give much more material than the class can possibly keep up with. This is a very common fault of lecturers who use slides. But cannot the remedy be simply effected by taking the difficulty into account? A fourth but minor objection is the comment that the use of slides calls for the service of a lantern operator. This problem is easily overcome. If one avoids the pitfall of going too fast and of using too many slides, any student can operate the lantern with a minimum of effort and without losing any of the lecture context. GUIDE NO-
Soon after the lantern-slide method of presentation was adopted, it became obvious that a set of guide notes to the lectures for student use, might be very helpful. The preparation of such a set of notes was undertaken with some trepidation. Not only would the proper development of the notes require considerable effort; but of greater concern was the possibility that their availability might reduce student incentive for attendance a t lectures. The format chosen for the notes was such as to lend itself to the presentation of lectures from slides. In general, a page of the notes corresponds to a single lecture, and is accompanied by eight to ten slides, and the development of such unit
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lectures--each dealing with a stated topic-has been a critical feature in the growth of the author's course. This purpose, to present each lecture as a suitable unit unto itself, has been well fostered by the preparation of the guide notes and by the manner in which they are used. A brief demonstration is also planned for each lecture, and a short period of discussion is often allowed at the close of the hour. The notes and the exercises which are supplied to the student are definitely not intended to supplant the textbook or the original literature; nor are they, by any means, graphic facsimiles of the oral lecture. Indeed they may be so planned and used as to assure that the student will use his book constantly while solving problems and reviewing his notes. By inclusion of appropriate exercises and references, the occasional reading of original articles is also encouraged. The lectures and demonstrations will mean most to the student only if he prepares for them carefully, both before and after the lecture period. No specific recommendations need be made a t this point, since this is a task which is quite entirely the responsibility of the student. We have, however, observed with interest the various study techniques which our students have developed to fit the preseut organization of the lectures; and we have been particularly impressed with the manner in which many of them have incorporated the printed notes with their own records of exercises and of class and reading notes into a quite comprehensive and useful compendium. The students still take a considerable number of notes during the lecture, but these are marginal ones--on critical points, or on new material over and above that already available for them in the printed notes or textbook. Although we are of the opinion that no lowering of standards, whatever, has been incurred by adopting the preseut mode of lecture presentation, we are well aware of the criticisms which may be levied against the use of such class notes as were described above. It is our belief, however, that the difficulties are not inherent in the fact that the notes are made available, but rather in the possibility that the major requirement of the course may become the rote memorization of such a set of notes, rather than their critical use toward a broader objective. Our experience strongly implies that the proper use of the notes and slides permits the instructor to conduct his lectures in a manner which impels the students to seek the truly important aspects of the course. In a good presentation of any subject, the lecturer must be free to observe his audience and to be with them; and he must permit his listeners to formulate questions in their minds. In this connection, the old rule for effective teaching, "First tell them what you are going to tell them about; then tell it to them; and then tell them that you have told it to them," can be a useful guide to good results if it is done lightly and with imagination. Visual aids as such certainly cannot lend the inspiration for a good lecture; but properly and simply used, they can free the lecturer to do his best work.
