XXXVlll INTRODUCTION. 



remaining heaped up above the brims of vessels ; and to their 

 attraction of cohesion, may be referred many phenomena in 

 evaporation and solution, their spontaneous ascent in capil- 

 lary tubes, whether natural or artificial, the motion of the 

 various juices through .animal bodies and vegetables, of water 

 through layers of ashes and sand or the rocky strata of the 

 earth and its ascent between plates of glass; to this attraction 

 may be referred solid bodies dissolving in fluids, whose first 

 colour or appearance is not changed, or changed without sen- 

 sible augmentation of the volume ; the mutual action of bodies 

 in contact with each other exhibiting this attraction, as when 

 dry salt of tartar is exposed to the air, it becomes fluid ; the 

 attraction of cohesion evinced in the process of evaporation, as 

 when the warm air of a room is crystallized on the panes of 

 glass during a cold night. We, however, are employed in con- 

 sidering the cohesion of water, which is known to be a com- 

 pound of hydrogen and oxygen, in the proportion of 15 parts 

 of the former, and 85 of the latter. Now this oxygen, which 

 exists in so large a proportion in water, makes exactly one-fourth 

 part of the atmospheric air which all animals breathe. It is 

 the pure part of the air, for the nitrogen or azotic gas which 

 exists in air, in the proportion of three-fourths, is incapable of 

 sustaining animal life or combustion for a single instant. The 

 atmosphere contains besides various supplementary matters, but 

 water is the most abundant, being there found in its different 

 states of cloud, mist, rain, dew, snow answering a thousand 

 useful purposes in the great laboratory of nature, so that upon 

 the whole there is a perfect balancing of actions, preserving 

 the atmospheric mass in a uniform state, constantly fit for its 

 admirable purposes of animal and vegetable existence. The 

 sea-water, however, contains besides hydrogen and oxygen, a 

 solution of muriate of soda, or table salt, which probably 

 adapts this fluid for the purposes of animal life ; at all events 

 preserves the ocean from putrefaction. That the oxygen of the 

 water does not by cohesion or absorption swallow up the 

 oxygen of the atmosphere, and leave the earth to be surrounded 

 with a covering of deadly azotic gas, is perhaps to be accounted 

 for by the general laws of electrical attraction and repulsion, 

 which as they respect the physical constitution of these two 



