Jeans on the Physical Sciences
POPULAR histories of science are few in number, and the news that the late Sir James Jeans had left the corrected proofs of such a work
raised hopes that a valuable addition to the existing literature would be made, notwithstanding that it was concerned only with the physical sciences. Sir James's lucidity of writing and skill in devising apt illustrations of difficult ideas are well known, and these qualities are no less useful in depicting the course of development of science than in elucidating the complexities of modern physical theory in which his success has been so marked. They are indeed to be found here. The story of the progress of astronomy, chemistry, mathe- matics and physics from the earliest times right up to the present is told in a straightforward manner, with judicious selection of the essential and considered balance of emphasis. An impression is given of the slow, almost incoherent beginnings, gradually expanding into the vastness and breathless speed of modern research, and we are left with a proper sense of the limitless regions yet to be explored. The pictorial illustrations are ample, excellent and well chosen.
All this is finely done, but it is unpleasant to have to add that the defects of the book are at least as conspicuous as its merits. One gets no feeling of the characteristic of science which may be described as a groping for something not seen but recognised when grasped—the characteristic which Tennyson expressed by saying that "science reaches forth her arms to feel from world to world." Lack of space, of course, would have been a sufficient reason for refusing to follow the many wrong tracks which are an intrinsic part of the history of science, but not for obscuring their existence. The course of scientific progress is not a preconceived, ordered move- ment in which each step inevitably determines the next ; and when, as here, not only are the divagations ignored but the true path is exhibited as though illuminated by knowledge which the pioneers did not possess, the picture becomes esseneally false. For example, we read: "Herschel now found that all the stars in one half of the sky appeared to be scattering apart, while those in the other half all appeared to be closing in on one another." The supposed fact is not even true for it is only statistically that the effect is shown, but the greatest discrepancy is that "all the stars in the sky" were in fact fourteen stars, for Herschel had only such exiguous data, and his conclusion was a brilliant conjecture favoured by remarkably good fortune. Again, in introducing the chemical families which guided Mendeleef in framing the periodic table, Sir James states that "the elements fall into groups in which all the members possess similar, though not identical, properties. There is, for instance, the group of the metals, and again the group of monatomic gases in which the atoms are so inert that they do not form compounds." The metals do not form a group in this sense, and Mendeleef knew nothing of the inert gases, which were not discovered until many years after- wards. In these and in other examples we see the expositor of prin- ciples triumphing over the recorder of facts. Herschel's conclusion, which we now believe to be true (though not the whole truth), is most easily explained by an imaginary model, and accordingly Jeans gives us the model as though it were actual and known to Herschel, and the same is true of Mendeliers work.
This habit of treating facts, natural or artificial, merely as instru- ments for the elucidation of principles which is as fatal a defect in a historian as in a scientist, is perhaps principles, outstanding feature of the book, evident not only in such instances as those just given but also in the disrespect shown to accuracy in general. There are numerous errors of dates, of names of persons and of titles of institutions, and even malapropisms, not to mention printing errors, and in the later sections there are such surprising misstatements violating even the principles enunciated that one cannot help suspecting undue haste
to get the job done. It would have been a pleasure to welcome a worthy conclusion to a noteworthy scientific life, but it would be improper to recommend the book to any who want more than a very broad picture of the way in which science has grown from small
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