On tJie Origin of Meteoric St(ynes, , 79 



particles by the minutest chinks and apertures ; and part of it 

 may in this way be accounted for. But there are other circutn? 

 stances which point to a different origin. Where dust is collects 

 ed in quantity, for instance, in a library, there is a peculiar smeli 

 perceptible ; are we not hence entitled to conclude that the dust 

 is rather a precipitation from the incumbent air, than something 

 conveyed thither by purely mechanical means .? When there is 

 another apartment adjoining to one filled with books, equally 

 closely shut, and left undisturbed for an equal period, dust will 

 be found in both, but neither of the same kind, nor having the 

 same smell, as ought to be the case were it merely admitted by 

 the apertures of the doors and windows. A library presents 

 still another argument for this hypothesis, which is, that the pa- 

 per of the books evidently undergoes, in process of time, a che- 

 mical change. It becomes yellow, friable, and lighter. Un- 

 questionably this change arises from certain component parts of 

 the paper becoming volatile, which no doubt occasions the pecu- 

 liar smell ; and why should it be impossible that these, while in 

 suspension, should be subjected to new transformations, and at 

 last be precipitated in the form of fine dust.? 



If observations of this kind do not establish the capability of 

 solid bodies to become volatile, at the usual temperature, it must 

 at least be conceded that this hypothesis does not belong to that 

 class which are purely the offspring of the fancy ; for it is sup- 

 ported on facts alone, although it cannot be deduced from them 

 with all the rigour of logical induction. 



If this hypothesis be provisionally adopted, till farther investi- 

 gation, we are necessarily compelled to form a very different re- 

 presentation of our atmosphere than that generally admitted ; 

 for then, not only its apparent elements, but an infinite variety 

 of gases and vapours unceasingly emitted from all fluid and solid 

 bodies, must also be admitted as entering into it. 



But where do these exhalations remain ? And why is k, that, 

 in that part of the atmosphere submitted to our examination, we 

 find only faint traces of inconsiderable quantities of them ? I 

 will first endeavour to answer this last question, and I believe this 

 may be done in a very direct manner, by taking into considera- 

 tion the extreme rarity of these exhalations. How incompre- 

 hensibly fine many of them are, is incontestibly exemplified by 



