VOYAGE OUTWARD. 21 



possesses a sovereign power of impulse. The presence of 

 electricity in dry air is manifest in experiments, wherein all 

 moisture must be carefully removed, else this celestial agent 

 does not appear. The immortal Franklin detected its pre- 

 sence in the clouds, and forced it to descend, from that 

 species or rather genus of cloud, nimbus, in which it is 

 usually concentrated ; and its presence, when in motion, is 

 famihar to every one experimenting with an electrical 

 machine, when as the cylinder is revolved, a wind is sensi- 

 bly felt if the hand is placed near the cylinder. The 

 presence of this principle in the clouds is very remarkable 

 during the formation of the cloud above mentioned, being 

 what is familiarly called the thunder cloud. 



Mr. Howard has lately laid do^vn a classification of the 

 clouds, by which this branch of natural history has been 

 signally simplified. The reader is requested to refer to that 

 ingenious gentleman's publication. His theory has been 

 also copied at length into Mr. Forster's book on Clouds,* 

 wherein many curious illustrations of this subject are in- 

 serted. As my applications were on a scale of more than 

 3,000 miles in extent, with a perfectly natural horizon 

 almost perpetually under observation, I trust that the details, 

 which shall be as brief as possible, will not be subjected to 

 a charge of presumption on the patience of the reader. 

 I may be also pardoned the expression of my o^vn feeling 

 * Researches about Atmospheric Phaenomena, by Thomas Forster, F.L.S. 



