24H WRITINGS OF JOSEPH HENRY. [1855- 



ascending the sides of a mountain into the region of the 

 clouds he has seen globules of water as large as small peas 

 floating in the air, which from their levity were evidently- 

 hollow spheres, similar to small soap bubbles. From this 

 observation the idea became prevalent that the water of a 

 cloud was in a vesicular condition, or in other words that 

 cloud consists of minute hollow spheres of liquid water filled 

 with air which is rendered more buoyant by the rarefaction 

 due to the heat of the sun ; and this opinion was strengthened 

 by the fact that clouds do not give a decomposition of the 

 rays of light sufficient to exhibit the phenomena of the rain- 

 bow. In what manner such a condition of water can be 

 produced and how it can be retained, has not, so far as we 

 are informed, been explained by an}'- principle of science. 

 A soap bubble soon becomes too thin to retain its globular 

 form, and is resolved into the condition of soap water. Ordi- 

 nary water is still more unstable and cannot be retained for 

 an instant in a hollow spherical form. We shall therefore be 

 on the safe side if we adopt an hypothesis apparently more 

 in accordance with known and established principles, and if 

 this does not furnish a logical account of all the phenomena 

 we must wait until further research or light from collateral 

 branches of science dispels the obscurity with which this 

 point may be involved. 



The suspension of the clouds can be explained by taking 

 into account the extreme minuteness of the particles of which 

 they are composed. In the case of mists which are some- 

 times formed at the surface of the earth and afterwards be- 

 come clouds in being elevated into the atmosphere by a wind 

 blowing between them and the earth, the particles are of such 

 extreme tenuity as to be invisible to the naked eye, and their 

 presence is rendered evident only by looking through a 

 stratum of considerable thickness. 



If particles of lycopodium (the sporules or seeds of the club- 

 moss) are dusted upon a flat glass they exhibit a series of colors, 

 when held between the eye and the light, produced by the inter- 

 ference of the waves of different rays of light. In order to pro- 

 duce this effect, the particles of lycopodium (as can be proved 



