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APRIL I 2, I

889.]

SCIENCE.

289

the explanation given in Science of March 29, I do not desire to cite here any experimental confirmation of the theory, nor do I consider that the results given by Professor Hazen in any way disprove the theory. Why one should expect to be able to use the same formula for cone-shaped paper cups as had been found applicable to hemispherical metal cups, or should be surprised at a difLETTERS TO THE EDITOR. per cent **'CorresAondents are requested to be as rief astpossible. The writer's name is ference of twentyexample ofless wind-velocity, does not appear.some Following the Professor Hazen, I intend to try in all cases required as jirof ofgood aith. The editor will be glad to Aublish any queries consonaxt with the character of experiments with hemispherical paper cups, and have thus far the journal. completed a set; but the pressure of other duties has not afforded Twenty cojies of the number conxtaining his communication will be furnishea me opportunity to do more as yet. C. F. MARVIN. free to any corresAondent on request. Washington, D.C., April 8. The Robinson Anemometer. So long as the anemometer law is purely empirical, it is doubtThe Metric System and Professional Teaching. less largely a matter of individual taste that one should prefer to THE committee appointed at the Cleveland meeting to consider use a series of ratios whose values, even within the limits of ordinary usage, range between infinity on one hand, and 2.89 on the the relations of chemistry to public instruction, naturally have their other, - a value which corresponds, according to Science of March attention called to the metric system of measures. No doubt the 22 (p. 227). to a wind-movement of 25 miles per hour. Neverthe- familiarity of the public with this system has much increased since less occasion may be taken at some future time to point out a i866, when the Act of Congress was passed making it legal; but possible error into which one is easily led by use of this variable recent conversations with parties who might be supposed well posted on the subject show some views that appear to the writer factor. It seems, my "explanation of the effect of a uniform wind blow- incorrect, and adapted to retard the adoption of a much-needed reing across a whirler upon which an anemometer is being tested is form. very surprising; " indeed, I have wondered myself that so simple A very prominent teacher of chemistry said he was not an advoan explanation had not been suggested long ago. That it is " en- cate of its general use, and that no time would be saved in the tirely untenable " cannot be admitted, since it is only made to ap- instruction of children by such adoption. The Metric Bureau, in pear so by my critic, who unfortunately omits from the very heart their leaflet, stated that " a year of the school-life of every child of the statement whose accuracy he questions. three very impor- would be saved by the adoption of this system." This statetant words. Nothing more than this need be said. I am well ment was made by teachers. I do not know its basis; but there aware, also, that " it has generally been considered that while these are, in the English system of tables we use, about fifty factors to cups [of the anemometer] never respond instantly to the wind, and be memorized. As there is but one factor in the metric system, continually lag behind while the wind is rising, yet their momen- and that the same as our system of numeration, necessarily fifty tum keeps them up, and about counterbalances this lagging while times as much time is required to learn English measures as metric. the wind dies down;" but that these effects about balance is ex- If the Society for Psychical Research can tell us the average time actly what does not occur, and therein is the novelty of the ex- required to memorize an idea, we should then know the saving of time in instruction, that would follow the adoption of the metric planation I have suggested. The substitute offered in Science of April 5 (p. 268) is based system. partly on an incorrect statement; namely, that a wind blowing An apothecary assured me that the adoption of parts by weight directly at right angles to the path along which an anemometer is in the new pharmacopceia, with which he connected in some way being carried will add its effect to that due to the motion of the the metric system, had, in his judgment, done great harm to the drug anemometer. If the writer means that the sum of the two separate business: for, he said, the wholesale manufacturers put on the effects are to be taken, he is entirely wrong. It is a simple question of outside of their bottles that one part of this extract, etc., with nine the resultant of two forces at right angles to each other, which is not parts distilled water (or required proportions), would make ten volthe sum of the two separate forces. With this as a partial basis, the umes of the officinal strength. The extreme simplicity of this explanation is developed, and the astonishing conclusion reached process, my friend argued, reduced the drug business, so far as that "1 the anemometer will be accelerated during more than three- intellectual qualifications are concerned, below the grocer, and the fourths of the rotation [presumably of the whirler], and retarded metric system was somehow held responsible. during less than one-fourth of it." Had the author, in accordance The metric system is in universal use by chemists. The arts of with the principle of the parallelogram of forces, found the result- medicine and pharmacy are dependent on chemistry for their matant of the two wind effects that act simultaneously upon the ane- terials and their processes. As matters now stand, every student mometer at each point of its path, and integrated or summed these in the colleges of these arts is obliged to learn two new tables of up for a complete revolution of the whirler, he would doubtless measures, - apothecary and metric; for I assume that all profeshave arrived at a much more accurate conclusion, - a conclusion sors of chemistry teach the metric, and some professors of materia that the ultimate resultant effect for a whole revolution "is only medica also. In other schools the chair of chemistry teaches one, small in most cases, and is not very serious," as given in my and the chair of materia medica the other system. original letter in Science of March 29; a view, moreover, that is Is it not time to inquire if this is a rational condition of things ? entertained by Professors Dines, Stokes, and others who happen to It will not do to say the apothecary weight is learned in the prihave written on the question. mary school. The metric is taught also, at the present time. Both Even admitting that the explanation under discussion is correct, are usually forgotten before the student matriculates. Neither can it does not account for the uniformity of the results obtained in it be said that we break away from the system of our English couEngland with the helicoid anemometer, which, being provided with sins, for our fluid measures are not the same as theirs, now that a vane or tail, always presented its front directly to the resultant they use the imperial gallon. There remains the single argument wind. The Robinson anemometer, from its construction, has no against the metric system in our professional schools, that it is not need of a tail, and the two instruments are circumstanced exactly in general use by physicians. Those who do use it find the gram alike so far as being equally subject to the resultant wind. It is a most convenient unit. The difficulty of inducing a large body of presumed throughout this and previous papers that the axis of the men to change some of their basic elements of thought seems to be Robinson anemometer is vertical or nearly at right angles to the the greatest obstacle to a beneficial improvement. plane of rotation of the whirler. The analysis of the problem is a Now, why not let the old doctors use the old system, but teach little different when the axis is inclined more or less to the vertical, the graduates only the new; then add to the pharmacy laws a but the final result is practically the same. clause requiring every druggist to provide himself with a set of Having several weeks ago submitted a paper containing in detail metric weights, making this condition as indispensable as a dithe various experiments and results that led to the development of ploma? At present, when a prescription is presented in the metcountries, while the second contains samples of all the articles which are manufactured in Belgium. A library and an information bureau are attached to this museum.

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