442 Notices respecting New Boohs. 



Sun, suggested to Sir William Huggins the possibility that this- 

 novel method of research might he extended to the other heavenly 

 bodies. He would find out whether, as required by Laplace's- 

 nebular hypothesis, the unity of the law governing their motion 

 had not its counterpart in the unity of their composition. Eager 

 to explore this virgin field, Sir William yet did not underestimate - 

 the great difficulties involved, and in the ' Papers ' before us we 

 find with what patience, perseverance, and fertility of resource 

 they were severally met and overcome. 



The first section relating to the observatory and instrument 

 is deserving of careful stucl}^, and illustrates the perfect adap- 

 tation of means to the end by many ingenious contrivances. It 

 must be remembered that at this time a Star Spectroscope was- 

 a thing unknown, and all the necessary details had to be supplied 

 by the inventive genius of the explorer. Amongst these contri- 

 vances may be mentioned the cylindrical lens for widening the 

 linear star spectrum into a band on which the lines might be seen ;.: 

 the polished slit of speculum metal whereby the slit itself was 

 made to serve in keeping the star image steadily on any part of it ;. 

 and the method of applying the comparison spectrum so as to 

 avoid a spurious shift of the lines. The advantage of a mirror of 

 speculum metal together with Iceland spar for the prisms and' 

 quartz for the lenses in photographing the more refrangible part 

 of the spectrum was also perceived and utilized. 



The first-fruits of Sir William's work were contained in a note- 

 to the Royal Society in 1863, " On the Lines of some of the 

 Pixed Stars," in which diagrams were given of the spectra of 

 Sirius, Betelgeux, and Aldebaran, showing the principal lines and! 

 their position relatively to the chief solar lines. This was followed 

 by a paper which appeared in the Philosophical Transactions for 

 1864, " On the Spectra of some of the Pixed Stars," in which are 

 given the results of a most careful comparison of the spectra of 

 Aldebaran and Betelgeux with the spectra of sixteen terrestrial 

 elements, as well as the result of the examination of several other- 

 stars, from which the author draws the inference that "a similar 

 unity of operation extends through the universe, as far as light 

 enables us to have cognizance of material objects. 



The importance of supplementing eye observations of the- 

 spectra of stars by photographs Avas so obvious, that as far back 

 as the year 1863 an attempt was made to obtain such photographs,, 

 but it was not until the introduction of the gelatine dry plate in 

 1875 that success in this direction was attained. Very notable 

 was the photograph of the spectrum of Yega taken in 1876,. 

 showing seven dark lines. A later photograph showed twelve 

 lines, and from their similarity and the symmetry of their arrange- 

 ment " the suggestion presents itself whether these lines are not 

 intimately connected with each other and present the spectrum of 

 one substance." Sir William observed that two of the lines 

 coincided with two known hydrogen lines in the solar spectrum, 

 but it was not till much later that so many as twelve of the series- 



