43 



HISTORY OF SCIENCE. 



FIG. 191. THE SPIRAL NEBULA. 



2,306 objects. The results of the observations which the same eminent 

 astronomer carried on at the Cape of Good Hope were published in 

 1847, and contained among other objects 1,708 nebulae. The most 

 valuable contributions that have since been made to our knowledge 

 of nebulae are due to Lord Rosse, whose observations have been made 

 by the great 6-feet reflector, which will be described on a subsequent 

 page. Many nebulae, which in telescopes of less power presented a 

 wholly cloudy appearance, were by Lord Rosse's powerful instrument 

 resolved into close clusters of stars. Other nebulae, not thus resolvable, 

 nevertheless present with the 6-feet reflector a very different aspect 

 to what they do with an 1 8-inch reflector. Nebulae are almost the 

 least luminous of celestial objects, and it will be readily understood 

 that details of their structure, invisible with the 1 8-inch reflector, are 

 revealed with the 6-feet instrument, which admits sixteen times as 

 much light as the other. Some of the most interesting observations 

 made by Lord Rosse are those of spiral nebulae. One of the most 

 remarkable of these is in the constellation Comes Venatici. It presented 

 to Sir J. Herschel the appearance of a bright globular cluster sur- 

 rounded by a ring, which he thought to be divided through about 

 half its circumference, while near it was a small, bright, round nebula. 

 Lord Rosse's telescope shows this object as a series of spirals of ne- 

 bulous matter, and the smaller nebula near is found to be connected 



