(55) *to 



with a dense cloud of sulphur particles, which by the 

 application of proper means may be rendered visible. 



Here, then, our ether waves untie the bond of chemi- 

 cal affinity, and liberate a body sulphur which at or- 

 dinary temperatures is a solid, and which therefore soon 

 becomes an object of the senses. We have first of all 

 the free atoms of sulphur, which are both invisible and 

 incompetent to stir the retina sensibly with scattered 

 light. But these atoms gradually coalesce and form 

 particles, which grow larger by continual accretion until 

 after a minute or two they appear as sky matter. In 

 this condition they are invisible themselves, but compe- 

 tent to send an amount of wave motion to the retina 

 sufficient to produce the firmamental blue. The parti- 

 cles continue, or may be caused to continue, in this con- 

 dition for a considerable time, during which no micro- 

 scope can cope with them. But they continually grow 

 larger, and pass by insensible gradations into the state of 

 cloud, when they can no longer elude the armed eye. 

 Thus, without solution of continuity, we start with mat- 

 ter in the molecule, and end with matter in the mass, 

 sky matter being the middle term of the series of trans- 

 formations. 



Instead of sulphurous acid we might choose from a 

 dozen other substances, and produce the same effect 

 with any of them. In the case of some probably in 

 the case of all it is possible to preserve matter in the 

 skyey condition for fifteen or twenty minutes under the 

 continual operation of the light. During these fifteen or 

 twenty minutes the particles are constantly growing 

 larger, without ever exceeding the size requisite to the 

 production of the celestial blue. Now when two ves- 

 sels are placed before you, each containing sky matter, 



