120 FEAGMENTS OF SCIENCE. 



will take an experiment suggested by some of my own 

 researches, and described by M. Morren of Marseilles 

 at the Exeter meeting of the British Association. 

 Sulphur and oxygen combine to form sulphurous acid 

 gas, two atoms of oxygen and one of sulphur consti- 

 tuting the molecule of sulphurous acid. It has been 

 recently shown that waves of ether issuing from a 

 strong source, such as the sun or the electric light, are 

 competent to shake asunder the atoms of gaseous mole- 

 cules. 1 A chemist would call this, ' decomposition ' by 

 light ; but it behoves us, who are examining the power 

 and function of the imagination, to keep constantly 

 before us the physical images which underlie our terms. 

 Therefore I say, sharply and definitely, that the compo- 

 nents of the molecules of sulphurous acid are shaken 

 asunder by the ether-waves. Enclosing sulphurous 

 acid in a suitable vessel, placing it in a dark room, and 

 sending through it a powerful beam of light, we at 

 first see nothing : the vessel containing the gas seems 

 as empty as a vacuum. Soon, however, along the 

 track of the beam a beautiful sky-blue colour is observed, 

 which is due to light scattered by the liberated parti- 

 cles of sulphur. For a time the blue grows more 

 intense ; it then becomes whitish ; and ends in a more 

 or less perfect white. When the action is continued 

 long enough, the tube is filled with a dense cloud of 

 sulphur particles, which by the application of proper 

 means may be rendered individually visible. 2 



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

 cal affinity, and liberate a body sulphur which at 



1 See ' New Chemical Ileaclions produced by Light,' vol. i. p. 



8 M. Morren was mistaken in supposing that a modicum of 

 sulphurous acid, in the drying tubes, had any share in the produc- 

 tion of the 'actinic clouds ' described by me. A beautiful case of 

 molecular instability in the presence of light is furnished bj 

 peroxide of chlorine as proved by Professor Dewar. 1878. 



