HYDROGE^sIUM. 
239 
element — hydrogen — forms an important constituent of the 
nebulous groups and cometary films., The examination of 
surface forces instructs us that the element which, oxidised, 
becotues water, and which, in its combinations with carbon, 
plays so important a part in the animal and vegetable economy, 
is no less essential as an agent modifying the conditions of the 
mineral world. From the stud}^ of little things — the solution 
of sugar, the absorption of water by a sponge — we are advanced 
to the discovery of truths which bear on the mysteries of mole- 
cular structure, and on the constitution of worlds in space. 
VOL. VIII.— NO. xxxii. 
R 
