162 DR. R. ANGUS SMITH ON A 



salt to a great distance. I have sometimes, in this case, 

 believed that I saw the proof of hollowness of such vesicles ; 

 and the great range of their flight is remarkable to any 

 one who will stand even in a large room where metal is 

 dissolving. I have sometimes found branches of trees, set 

 a considerable distance from works where sulphate of iron 

 was manufactured, so covered with crystals as to be striking 

 to passers-by. This observation of the balloon-forming cha- 

 racter in the evolution of hydrogen gas was first made to 

 me by my friend James Higgin, F.C.S. 



This observation, however, is entirely independent of 

 any thing that we know to occur in the regions of the air 

 where cloud is formed. The remarkable vapour which 

 was described at the beginning, and which led me to look 

 a little into this subject, showed me no signs of vesicularity 

 where one would have supposed there existed the best 

 opportunity of seeing it. 



That there are difficulties attendant on the explanations 

 of the subsistence of vapour, it is easy to see; but vesicles 

 of any kind we can suppose must be heavier than the air 

 around them, and even the inventors have been aware of 

 the new difficulty, and sought to lift them up by various 

 means. They have probably arisen out of the imagination 

 of people active-minded and speculative, and been seen 

 by the eyes of persons whose reasonings were beforehand 

 affected with the notion. If vesicles should be found (and 

 who knows what wonderful things there may be found in 

 the future ?) , the discovery must have an entirely new origin 

 and basis. 



Indeed I see no reason for going far for a mode of keep- 

 ing clouds up. Times out of number I have observed on 

 calm summer evenings a cloud of smoke from a steamboat- 

 funnel, lying for miles in length at a height very little dif- 

 ferent from that of the funnel out of which it issued. 

 Sometimes this will be found a little lower. At other 



