THE CHEMICAL ELEMENTS. 327 



of the mercury in the tube of a barometer, known as the 

 Torricellian vacuum, is filled with the vapour of mer- 

 cury. There is, therefore, no reason why nitrogen, or 

 even hydrogen, should not be metallic molecules kept 

 by the force of the repulsive powers of heat, or some 

 other influence, at a great distance from each other. 

 The peculiar manner in which nitrogen unites with mer- 

 cury, and the property which hydrogen possesses of 

 combining with antimony, zinc, arsenic, potassium, 

 sodium, and possibly other metals, besides its union with 

 sulphur and carbon in all which cases there is no such 

 change of character as occurs when they combine with 

 oxygen appear to indicate bodies which, chemically, are 

 not very dissimilar to those metals themselves, although, 

 physically, they have not the most remote resemblance. 



" We know nothing," says Davy, " of the true ele- 

 ments belonging to nature ; but, so far as we can reason 

 from the relations of the properties of matter, hydrogen 

 is the substance which approaches nearest to what the 

 elements may be supposed to be. It has energetic powers 

 of combination, its parts are highly repulsive as to each 

 other, and attractive of the particles of other matter ; it 

 enters into combination in a quantity very much smaller 

 than any other substance, and in this respect it is 

 approached by no known body."* 



Many of the elements are common to the three king- 

 doms of nature : most of those found in one condition ot 

 organization are discovered in another. The carbonates 

 are an abundant mineral class. In the vegetable kingdom 

 we find carbon combining with oxygen, hydrogen, and 

 nitrogen : these elements, also, constitute the substance 

 of animals, the proportion of nitrogen being, however, 

 much larger. If one element, more than another, be- 

 longs especially to the animal economy, it is phosphorus, 

 although this is not wanting in the vegetable world; 



* Elements of Chemical Philosophy : by Sir H. Davy. 



