594 PHILOSOPHICAL TRANSACTIONS. [aNNO I789. 



another which takes in a range of a million. Youth and age are comparative ex- 

 pressions ; and an oak of a certain age may be called very young, while a co- 

 temporary shrub is already on the verge of its decay. The method of judging 

 with some assurance of the condition of any sidereal system, may perhaps not 

 improperly be drawn from the standard before laid down page 589 J so that, for 

 instance, a cluster or nebula which is very gradually more compressed and bright 

 towards the middle, may be in the perfection of its growth, when another which 

 approaches to the condition pointed out by a more equal compression, such as 

 the nebulae I have called planetary seem to present us with, may be considered 

 as very aged, and drawing on towards a period of change, or dissolution. This 

 has been before surmised, when, in a former paper, I considered the uncom- 

 mon degree of compression that must prevail in a nebula to give it a planetary 

 aspect ; but the argument, which is now drawn from the powers that have col- 

 lected the formerly scattered stars to the form we find they have assumed, must 

 greatly corroborate that sentiment. 



This method of viewing the heavens seems to throw them into a new kind of 

 light. They now are seen to resemble a luxuriant garden, which contains the 

 greatest variety of productions, in different flourishing beds ; and one advantage 

 we may at least reap from it is, that we can, as it were, extend the range of our 

 experience to an immense duration. For, to continue the simile I have borrowed 

 from the vegetable kingdom, is it not almost the same thing, whether we live 

 successively to witness the germination, blooming, foliage, fecundity, fading, 

 withering, and corruption of a plant, or whether a vast number of specimens, 

 selected from every stage through which the plant passes in the course of its 

 existence, be brought at once to our view ? 



Dr. H. then adds the catalogue of the 1000 new nebulae and clusters of stars, 

 the numbers, dates of observation, nanies, situations, and several other charac- 

 teristic circumstances, are arranged in 8 columns of a table, which is divided 

 into 8 classes or collections: — 1. The 1st class is of such as are titled, from 

 their appearance in the heavens, bright nebulae; the 2d class are the faint 

 nebulge ; the 3d class, the very faint nebulae ; the 4th class, planetary nebulae ; 

 the 5th class, very large nebulae ; the 6th class, very compressed, and clusters 

 of stars ; the 7 th class, pretty much compressed clusters of large or small stars ; 

 and the 8th or last class, coarsely scattered clusters of stars. To the catalogue 

 Dr. H. adds the following postscript, to announce a newly discovered satellite of 

 the planet Saturn. 



p. s. The planet Saturn has a 6th satellite revolving round it in about 32^ 

 48"". Its orbit lies exactly in the plane of the ring, and within that of the 1st 

 satellite. An account of its discovery with the 40 feet reflector, and a more 

 accurate determination of its revolution and distance from the planet, will be 

 presented to the r. s. at their next meetings. 



