THE 



POPULAR SCIENCE 

 MONTHLY. 



JULY, 1874. 



TELESCOPIC RESEARCH ON THE NEBULA OF ORION. 



By EDWARD S. HOLDEN, 



PROFESSOR IN THE UNITED STATCS NAVAL OBSERVATORY AT WASHINGTON. 



IT is well occasionally to cast our eyes back over a series of labors, 

 in order that we may rightly judge of our progress. 



Rough comparisons alone will not tell us : it is easy to contrast 

 Galileo's piece of lead-tubing, having a lens in each end of it, with 

 the gigantic telescopes of to-day; but we hardly learn much from 

 such a comparison. The extremes of the series are too far removed; 

 to get a just idea of the terms between, the comj^arisons must be made 

 at shorter intervals. 



If we can select some celestial object, which has been telescopically 

 studied for a long period, we may, by contrasting the results obtained 

 at different times, gain some accurate notion of the progress made, 

 and of the way in which it was made. 



This latter idea is of some importance when we consider that the 

 day of startling discoveries is over. When Galileo found the four 

 moons of Jupiter, the whole world of men of learning was astounded ; 

 and still more wonderful was his discovery of the ring of Saturn — 

 that is to say, of the existence of a ring of Saturn — a portion of 

 which, showing on each side of the planet, gave to Saturn the " tri- 

 corporate" aspect which Galileo describes in a letter to his friend 

 Kepler, 



Even the discovery of Uranus by Sir William Herschel, in 1789, 

 was by no means an extraordinary event, although it was received 

 with enthusiasm in all Europe, for Herschel's examination of the 

 heavens was done with the aid of an instrument which could not fail 

 to show Uranus with a sensible disk, if the planet should enter the 

 field of his telescope. 



The discovery of the first asteroid, Ceres, on the 1st day of Jan- 

 uary, 1801, by Piazzi, was received with some surprise, but these 

 small bodies have lately become quite common (there being now 135 



VOL. V. — 17 



