158 DR. R. ANGUS SMITH ON A 



It is clear that, in this, Hamberger has found a possible 

 way of raising vapours and of keeping them afloat ; whereas 

 the others have wandered more amongst vapours heated 

 internally, which we know must soon equalize their heat ; 

 heat-particles have also led some astray. 



We may, in reality, say that amongst those who seem 

 to have been the founders of this theory of vesicles, no 

 reasons have been given, but only a few fancies by no 

 means well supported even in the opinion of the authors, 

 and still less in that of natural philosophers at the present 

 time. 



We may conclude that a drop of water may be rendered 

 more easily supported and moved in the air by two 

 methods easily imagined : — the first, namely, by increasing 

 the size in the vesicular method; the second, by being 

 broken into minute fragments. In clouds we may sup- 

 pose either cause ; but no reason is given for the first, and 

 we must fall back on the second. These fragments are of 

 various sizes. 



I have not searched carefully the authors who have taken 

 up the subject of vesicles, and do not think it well to 

 spend much time upon it ; but Horace-Benedict de Saus- 

 sure, being the most notable, and the one to whom the 

 idea itself is generally referred, must be carefully attended 

 to. In his ' Essais sur THygrometrie ' there is a chapter 

 on " Vesicular and Concrete Vapours," at page 282. A 

 few of the most characteristic sentences will be given. 



Par. 199. "If there is no body contiguous to that air 

 which is supersaturated with vapour, so that it may attach 

 itself, the elements of water unite together and form 

 either small spherical full drops, or small congealed 

 needles, or, finally, hollow spheres." 



200. " These little solid drops, which unite to form rain 

 and the frozen needles (the first rudiments of snow) , may be 

 considered not to be vapours ; but as they are so fine as to 



