CURRENT LITERATURE.
for geometry, has recognised certain errors of statement, which, instead of convincing him that he should study only works by writers of repute, have unfortunately misled him to invent new theories of phenomena already understood. This is a roundabout way of saying that Lieutenant- Colonel Drayson has become a paradoxist, a fate which has befallen others, who, like him, have a moderate knowledge of mathematics. It is unfortunate for the Astronomical Society, that its ranks are not free from paradoxists of mathematical tastes, the most mischievous of the order because they are enabled to accompany false theories in physics with the correct manipulation of formulas or of geometrical relations. Perigal, the opponent of lunar rotation, is an instance in kind, since, despite the absurdity of the physical theory he seeks to establish, he is an excellent geometrician, and probably better acquainted with the various forms of looped and cyclic curves which can be traced by mechanical means than any mathematician living. The work before us illustrates De Morgan's criterion for distinguishing between the paradoxist and the discoverer of new truths. A Copernicus, a Kepler, a Herschel, like a Drayson or a Perigal, advances views differing from those which had been before entertained. But the discoverer of new truth shows a perfect familiarity with the theories which had before his day been believed in ; or where no theories had been regarded as established, goes thoroughly over the ground, and ascertains many new facts before he ventures to enunciate new ideas. We find Copernicus devoting half his working life to the study of the various theories of the planetary system before he enunciated the Copernican theory, Kepler analysing for a score of years the effects of epicyclio motion before he discovered the law of elliptic motion, while Sir W. Herschel based his new theories of the heavens on a survey altogether more complete than any which his predecessors had carried out. And so of all real discoverers or just theorisers in science. But a paradoxist prepares otherwise for his feats. Colonel Drayson is now the author of three parodoxical works, all closely related together, since all are based on his original misapprehension. Most of the text-books of astronomy assert that the pole of the heavens circuits around the pole of the ecliptic in about 25,860 years, and nearly all star-charts (Colonel Drayson says all, but this is far from being the case) show a circle which is marked as that wherein the pole of the heavens so travels. The truth is that this motion, although for long intervals of time together it differs little in character from motion in such a circle, is not in reality completed in the circle mentioned. The pole of the ecliptic is, in fact, continually, though slowly, changing, owing to the change which is continually taking place in the position of the earth's path on account of the perturbing influences of the other planets. The only unchanging point on the celestial heavens, so far as the solar system is concerned, is the pole of what Laplace (who first demonstrated the fact) called the "invariable plane." This point lies more than a degree and a half from the pole of the ecliptic ; but though fixed, it is not the centre around which any other polar point revolves. Now, of this invariable plane Colonel Drayson has apparently never heard, nor is he acquainted with the physical reasoning by which both the motion of the pole of the earth and that of the ecliptic pole are explained. But having found out by geometrical reasoning that the pole of the equator is not performing a complete circle around the pole of the ecliptic, as the text-books say, he imagines that he had made a great discovery; and by a process of geometrical reasoning, applied with considerable acumen and accuracy to the observed motion of the pole during the last few hundred years, on the assumption that the motion is in some circle about some centre, he finds that centre to be six degrees from the pole of the ecliptic. His first book enun- ciated this result. Of course, if the centre around which the pole of the heavens circuits were thus eccentric with respect to tho pole of the ecliptic, the obliquity of the ecliptic would vary six degrees on either side of the mean value, and hence there would result numerous climatic changes. Thus, according to due paradoxical progression, we derive an explanation of the glacial epoch, its date, duration, and so on. This forms Colonel Drayson's second book. A third consequence of his unfor- tunate discovery is the recognition of the fact that certain changes would result in the apparent right ascension of the stars, differing somewhat from those taking place on the accepted theory ; and the idea suggests itself naturally enough that the proper motion of the stars
may be explained in this way. To a paradoxist, little familiar with the array of ascertained facts which would keep the thorough student from such an attempt, the task of reconciling the proper motions with this suggestion seems easy enough : and with fatal facility Colonel Drayson accomplishes it in this, his third volume, which, as a con- tribution to science, is as valueless as the two former, though inter- esting to the student of paradoxism. And even as the squarer of the circle Is prepared to throw in as an appendix a new theory of terrestrial mag- netism, of cosmogony, or the like, so Colonel Drayson, having disposed paradoxically of the stellar proper motions, is prepared to throw in a new theory of the 'acceleration of the moon's mean motion,' with the real history of which he shows himself altogether unfamiliar.
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