NEBULA, CLUSTERS, ETC. 27 



Herschel, W. : Abstracts of Memoirs — Continued. 



A D. Vol. P. 



1811 101 309-310 Nebulous matter is probably capable of being consoli- 

 dated ; the act of shining proves it to have chemical 

 properties. 

 It will stop light, and is partly opaque. 

 311 Queries relating to the subsidence of the nebulous matter, 



the zodiacal light, and the cause of rotatory motion. 

 313 Some part of the nebulous matter is probably elastic. 



313 The uniform light of nuclei, and of much condensed 



nebulas, proves that the nebulous matter is considerably 

 opaque. 



314 When the nebulous matter assumes hardness, the progress 



of condensation will be impeded. 



315 Three indications of the compression of the nebulous mat- 



ter. 

 Planetary appearance arises from superficial lustre. 



316 High degree of condensation of the nebulous matter. 

 A still higher degree of condensation. 



318 In common good telescopes planetary nebulas cannot be 



distinguished from stars. 

 Perhaps they may in the end be so condensed as actually 

 to become stars. 



319 The nebulous matter in a cubical space of 10 / will admit 



of a condensation of two trillion and 208 thousand billion 



times before it can go into the compass of a globe of the 



diameter of our sun. 

 Planetary nebulas have a rotatory motion on their axes. 

 The original eccentricity of the nebulous matter of a 



nebula may be the physical cause of the rotatory motion 



of celestial bodies. 



320 The nebulous star in Orion is fictitious. 



321 Two out of three nebulous stars in Orion have lost their 



former nebulous appearance. 

 Their fictitious appearance was owing to a dispersion of 

 their light in passing through nebulous matter. 



322 The faintest appearance of the nebulosity in Orion is per- 



haps not further from us than the stars of the third or 

 second magnitude; the brightest part is therefore proba- 

 bly not so far. 



323 In thirty-seven years the nebulosity of this nebula has un- 



dergone great changes, and much greater since the time 

 of Huygheks. 



324 Nebulas are not permanent celestial bodies. 



325 Additional proof of the opacity of the nebulous matter. 



