356 A Short History of Astronomy [CH. xm. 



which dominate so much of astronomy and render it 

 unattractive or inaccessible to many. Moreover, not only 

 can descriptive astronomy be appreciated and studied, but 

 its progress can materially be assisted, by observers who 

 have neither knowledge of higher mathematics nor any 

 elaborate instrumental equipment. 



Accordingly, while the successors of Laplace and Bradley 

 have been for the most part astronomers by profession, 

 attached to public observatories or to universities, an 

 immense mass of valuable descriptive work has been done 

 by amateurs who, like Herschel in the earlier part of his 

 career, have had to devote a large part of their energies to 

 professional work of other kinds, and who, though in some 

 cases provided with the best of instruments, have in many 

 others been furnished with only a slender instrumental 

 outfit. For these and other reasons one of the most 

 notable features of nineteenth century astronomy has been 

 a great development, particularly in this country and in the 

 United States, of general interest in the subject, and the 

 establishment of a large number of private observatories 

 devoted almost entirely to the study of special branches of 

 descriptive astronomy. The nineteenth century has ac- 

 cordingly witnessed the acquisition of an unprecedented 

 amount of detailed astronomical knowledge. But the 

 wealth of material thus accumulated has outrun our powers 

 of interpretation, and in a number of cases our knowledge 

 of some particular department of descriptive astronomy 

 consists, on the one hand of an immense series of careful 

 observations, and on the other of one or more highly 

 speculative theories, seldom capable of explaining more 

 than a small portion of the observed facts. 



In dealing with the progress of modern descriptive 

 astronomy the proverbial difficulty of seeing the wood on 

 account of the trees is therefore unusually great. To give 

 an account within the limits of a single chapter of even the 

 most important facts added to our knowledge would be a 

 hopeless endeavour ; fortunately it would also be superfluous, 

 as they are to be found in many easily accessible textbooks 

 on astronomy, or in treatises on special parts of the subject. 

 All that can be attempted is to give some account of the 

 chief lines on which progress has been made, and to 



