Transformation of Nehulct into Stars. 321 



tinually engenders stars, why is it not exhausted ? Why does 

 the zone which contains it appear not to have diminished since 

 the time of Ptolemy ? This difficulty truly contains nothing 

 important : what means have we of knowing in what state the 

 Milky Way was 1500 years ago ? 



Of the condensation the diffused matter must undergo in order 

 to he transformed into Stars. — The opponents of the great ideas 

 I have referred to, seem to have entered upon a more serious 

 field of objections, when., founding their opinion on the exces- 

 sive rarity of the diffused matter, they assure us that the 

 whole of this matter observed in all the regions of space, 

 would not compose a star comparable to our sun in size and 

 density. A calculation of Herschel's has reduced the diffi- 

 culty to its true value. 



Let us take a cubical agglomeration of nebulous matter, the 

 side of which, seen from the earth, subtends only an angle of 

 ten minutes. Let us suppose that this agglomeration is situated 

 in the region of stars of the eighth or ninth magnitude. The 

 calculation will shew, that its volume will rise to more than 

 two trillions of times that of the sun. This result may be put 

 in this other form : the diffused matter contained in the cube of 

 10' the side, after having been condensed more than two tril- 

 lions of times, would still occupy as large a volume as our 

 sun. Now, have these objectors reflected on the condensa- 

 tion expressed by the prodigious number of two trillions ? 

 The objections against the actual production of stars, founded 

 on the rarity of the diffused matter, may therefore be set en- 

 tirely aside. 



Comparative iti tensities of the total light of a Nebula^ and the 

 condensed light of a Star. — After having examined the ques- 

 tions of volume and density, it ought to be asked if the feeble 

 scattered light of a nebula would be sufficient to produce, by 

 means of concentration, the lively, penetrating, scintillating 

 light of a star X 



Herschel, I believe, never studied the problem in this light. 

 But, if I am not mistaken, it may be illustrated in a few 

 words. 



