ARTICLE XIII. 



Observations on Nehulce with a Fourteen Feet Reflector, made hj H. L. Smith 

 and E. P. Mason, during the year 1839. By E. P. Mason. Read April 17, 

 1840. 



1. Although a period of nearly fifty years has now elapsed since the re- 

 searches of the elder Herschel exposed to us the wide distribution of nebulous 

 matter through the universe, we are still almost as ignorant as ever of its nature 

 and intention. The same lapse of time that, among his extensive lists of double 

 stars, has revealed to us the revolution of sun around sun, and given us a par- 

 tial insight into the internal economy of those remote sidereal systems, has 

 been apparently insufficient to discover any changes of a definite character in 

 the nebulas, and thereby to inform us at all of their past history, the form of 

 their original creation, or their future destiny. At the same time, the detection 

 of such changes is in the highest degree desirable, since no other sources of 

 evidence can be safely relied upon in these inquiries. That the efforts of as- 

 tronomers have thus far ended, at best, in vague and contradictory conjectures, 

 is principally attributable to the great difficulty of originally observing, and of 

 describing to future observers, bodies so shapeless and indeterminate in their 

 forms, with the requisite precision. For, we cannot doubt, authorized as we 

 are to extend the laws of gravitation far into the recesses of space, that these 

 masses of diffused matter are actually undergoing vast revolutions in form and 

 constitution. The main object of this paper is to inquire how far that minute 

 accuracy which has achieved such signal discoveries in the allied department 

 of " the double stars," may be introduced into the observation of nebulae, by 



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