These facilities, coupled with the wide and fascinating field of research opened up by Sir William Herschel's discovery of the binary character of double stars, gave an impulse to micrometric research which has continued unabated to the present time.
In attempting to pronounce on the evidence with regard to Herschel's theory, we must at once admit that the transmutation of a nebula into a star has never been seen.
It is indeed very doubtful whether any changes of a nebula have ever been seen which are of the same character as the changes Herschel's theory would require.
The same thought appears in a review of Herschel's Natural Philosophy, written about the same time.
Science, 1825); Herschel's instrument has since been discarded in favour of the pyrheliometer (Gr.
Some curious examples of echo are given in Herschel's article on " Sound " in the Encyclopaedia Metropolitana, but it appears that he is in error in one case.
In September 1839 a 3-foot speculum was finished and mounted on an altazimuth stand similar to Herschel's; but, though the definition of the images was good (except that the diffraction at the joints of the speculum caused minute rays in the case of a very bright star), and its peculiar skeleton form allowed the speculum to follow atmospheric changes of temperature very quickly, Lord Rosse decided to cast a solid 3-foot speculum.
The results of these skilfully conducted observations were published in a memoir on The Uranian and Neptunian Systems. 3 From this research it appears that the orbits of all four satellites of Uranus are sensibly circular, and although no special search was made, he concludes that none of Sir William Herschel's supposed outer satellites can have any real existence.
Freedom from aberration for two axis points, one of which is infinitely distant, is known as " Herschel's condition."
Herschel's Memoir of F.