146 FRAGMENTS OF SCIENCE. 



Brticke, I may say, also found the particles to be of ultra- 

 microscopic magnitude. 



But we have it in our power to imitate far more closely 

 than we have hitherto done the natural conditions of this 

 problem. We can generate in air, as many of you know, 

 artificial skies, and prove their perfect identity with the 

 natural one, as regards the exhibition of a number of 

 wholly unexpected phenomena. By a continuous process 

 of growth, moreover, we are able to connect sky-matter, 

 if I may use the term, with molecular matter on the one 

 side, and with molar matter, or matter in sensible masses, 

 on the other. In illustration of this, I will take an ex- 

 periment described by M. Morren of Marseilles at the last 

 meeting of the British Association. Sulphur and oxygen 

 combine to form sulphurous acid gas. It is this choking 

 gas that is smelt when a sulphur-match is burnt in air. 

 Two atoms of oxygen and one of sulphur constitute the 

 molecule of sulphurous acid. Now it has been recently 

 shown in a great number of instances 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 molecules. A chemist would call this " decom- 

 position" by light; but it behooves us, who are examin- 

 ing 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 components of the molecules of sulphurous acid are 

 shaken asunder by the ether-waves. Enclosing the sub- 

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

 sending through it a powerful beam of light, Ave at first 

 see nothing : the vessel containing the gas is as enrpty 

 as a vacuum. Soon, however, along the track of the 

 beam a beautiful sky-blue color is observed, Avhich is 

 due to the liberated particles of sulphur. For a time 

 the blue grows more intense ; it then becomes whitish ; 



