AIDS TO THE NEWTONIAN PERIOD. 487 



Milky Way in different places, apparently from some principle of Attrac- 

 tion ; and in this, and in one in 1817, lie published those remarkably 

 views on. the distribution of the stars in our own cluster as forming; a 



O 



large stratum, and on the connection of stars and nebulas (the stars ap- 

 pearing sometimes to be accompanied by nebulae, sometimes to have ab- 

 sorbed a part of the nebula, and sometimes to have been formed from 

 nebulae), which have been accepted and propounded by others as the JVeb- 

 ular Theory. Sir William Herschel's last paper was a Catalogue of 145 

 new Double Stars communicated to the Astronomical Society in 1822. 

 In 1827 M. Struve, of Dorpat (in Russia), published his Catalogue 

 Novus, containing the places of 3112 double stars. While this was 

 going on, Sir John Herschel and Sir James South published (in the 

 Phil. Trans. 1824) accurate measures of 380 Double and Triple Stars, 

 to which Sir J. South afterwards added 458. Mr. Dunlop published 

 measures of 253 Southern Double Stars. Other Observations have been 

 published by Capt. Smyth, Mr. Dawes, &c. The great work of Struve, 

 Mensurce Micrometricce, &c., contains 3134 such objects, including most 

 of Sir W. Herschel's Double Stars. Sir J. Herschel in 1826, 7, and 8 

 presented to the Astronomical Society about 1000 measures of Double 

 Stars; and in 1830, good measures of 1236, made with his 20-feet re- 

 flector. His paper in vol. v. of the Ast. Soc. Mem., besides measures 

 of 364 such stars, exhibits all the most striking results, as to the mo- 

 tion of Double Stars, which have yet been obtained. In 1835 he car- 

 ried his 20-feet reflector to the Cape of Good Hope for the purpose of 

 completing the survey of Double Stars and Nebulas in the southern 

 hemisphere with the same instruments which had explored the north- 

 ern skies. He returned from the Cape in 1838, and is now (1846) 

 about to give the world the results of his labors. Besides the stars 

 just mentioned, his work will contain from 1500 to 2000 additional 

 double stars; making a gross number of above 8000; in which of 

 course are included a number of objects of no great scientific interest, 

 but in which also are contained the materials of the most important 

 discoveries which remain to be made by astronomers. The publica- 

 tion of Sir John Herschel's great work upon Double Stars and Nebula? 

 is looked for with eager interest by astronomers. 



Of the observations- of Nebulae we may say what has just been said 

 if the observations of Double Stars; that they probably contain the 

 materials of important future discoveries. It is impossible not to re- 

 gard these phenomena with reference to the Nebular Hypothesis, 

 which has been propounded by Laplace, and much more strongly in 



