By T.S.H. EYTINGE, Cainsville, Canada.
It is well known that the sun's distance has been determined from the velocity of light. It has been found, by terrrestrial experiments, about how fast light travels, and, knowing from certain astronomical phenomena the time light requires to pass from the sun to the earth, we have been able to determine the sun's distance.
There are several methods of determining the velocity of light, but hitherto only two plans have been used to detect the time light occupies in passing from the sun to the earth. This time was first discovered by observations of the satellites of Jupiter. It was found that the interval between the eclipses of these bodies was not always the same--that the eclipses occurred earlier when Jupiter was nearest the earth, and later when he was at his greatest distance. Roemer, a Danish astronomer, first detected the cause of this variation. The second method by which this time has been found is the aberration of stellar light. This refined method was detected by the great English astronomer Bradley.
About two years ago it occurred to me that a third method can be used to solve this important problem. My plan is this: It is well known that many variable stars, such as Algol, σ Librae, U Coronae, and the remarkable variable D.M. + 1.3408°, discovered by Mr. E.F. Sawyer, fluctuate at regular intervals. Now, I believe it is possible to determine very accurately the intervals between these changes, and, by noting the change of time in these intervals, when the earth is in different points of its orbit, we get the time light requires to cross that orbit. For, as in the case of the satellites of Jupiter, when the star is "in opposition," the changes will occur earlier than when it is in conjunction or approaching that point. I have recently put this plan to the test, and hope before long to make known the results.
In detecting the changes of variables, I have attempted to substitute, in place of the ordinary eye observations, a very delicate thermopile, which registers the changes in the star's heat. So far as I know, this is the first application of the thermopile to variables.
PROFESSOR HAECKEL ON DARWIN.
In Nature appears a report of the remarkable address given by Professor Haeckel at the recent Eisenach meeting of the German Association of Naturalists on the theories of Darwin, Goethe, and Lamarck. The address is mainly devoted to Darwin and Darwinism, and of both, we need scarcely say, Professor Haeckel has the highest estimate. He said:
"When, five months ago, the sad intelligence reached us by telegraph from England that on April 19 Charles Darwin had concluded his life of rich activity there thrilled with rare unanimity through the whole scientific world the feeling of an irreparable loss. Not only did the innumerable adherents and scholars of the great naturalist lament the decease of the head master who had guided them, but even the most esteemed of his opponents had to confess that one of the most significant and influential spirits of the century had departed. This universal sentiment found its most eloquent expression in the fact that immediately after his death the English newspapers of all parties, and pre-eminently his Conservative opponents, demanded that the burial-place of the deceased should be in the Valhalla of Great Britain, the national Temple of Fame, Westminster Abbey; and there, in point of fact, he found his last resting-place by the side of the kindred-minded Newton. In no country of the world, however, England not excepted, has the reforming doctrine of Darwin met with so much living interest or evoked such a storm of writings, for and against, as in Germany. It is, therefore, only a debt of honor we pay if at this year's assembly of German naturalists and physicians we gratefully call to remembrance the mighty genius who has departed, and bring home to our minds the loftiness of the theory of nature to which he has elevated us. And what place in the world could be more appropriate for rendering this service of thanks than Eisenach, with its Wartburg, this stronghold of free inquiry and free opinion! As in this sacred spot 360 years ago Martin Luther, by his reform of the Church in its head and members, introduced a new era in the history of civilization, so in our days has Charles Darwin, by his reform of the doctrine of development, constrained the whole perception, thought, and volition of mankind into new and higher courses. It is true that personally, both in his character and influence, Darwin has more affinity to the meek and mild Melanchthon than to the powerful and inspired Luther. In the scope and importance, however, of their great work of reformation the two cases were entirely parallel, and in both the success marks a new epoch in the development of the human mind. Consider, first, the irrefragable fact of the unexampled success which Darwin's reform of science has achieved in the short space of 23 years! for never before since the beginning of human science has any new theory penetrated so deeply to the foundation of the whole domain of knowledge or so deeply affected the most cherished personal convictions of individual students; never before has a new theory called forth such vehement opposition and so completely overcome it in such short time. The depicture of the astounding revolution which Darwin has accomplished in the minds of men in their entire view of nature and conception of the world will form an interesting chapter in the future history of the doctrine of development."