-1859] WRITINGS OF JOSEPH HENRY. Ill 



A glance at this table will show the justice of the remark 

 of M. Dumas, that granting matter to be atomic it must 

 necessarily combine as it is found to do in this instance. 

 We refer to any work on chemistry for a table of atomic 

 weights, and shall only give here those of the atoms which 

 form the principal part of animal and vegetable bodies, 

 namely, hydrogen, carbon, oxygen, and nitrogen: 



Atomic weight. 



Hydrogen 1 



Carbon 6 



Oxygen 8 



Nitrogen 14 



To these, in lesser quantities, are added sulphur, 16; phos- 

 phorus, 32. We may say therefore that the whole atomic 

 system of animal and vegetable physiology depends princi- 

 pally on the four numbers 1, 6, 7, 8. Wherever the sub- 

 stances above mentioned are found in combination in any 

 of the three kingdoms of nature, they always combine ac- 

 cording to these numbers, or multiples of them — a statement 

 which contains in a single line a truth of the widest signifi- 

 cance; which has rendered chemistry an almost mathemat- 

 ical science, and its applications to agriculture an art of the 

 highest value and yet of comparatively easy attainment. To 

 facilitate still more the use of this generalization, the atoms 

 are expressed in abbreviated language. Thus water is rep- 

 resented by HO — that is, one atom of hydrogen, 1, and one 

 of oxygen, 8, making nine for the weight of the liquid. 

 Two atoms of water would be represented by 2 HO; car- 

 bonic acid by CO2, or one atom of carbon, 6, and two atoms, 

 of oxygen, 16; making for the atomic weight of the acid 22. 

 Nitric acid is represented by NO5, and ammonia by NH3, and 

 nitrate of ammonia by NOj+NHj; indicating, in the forma- 

 tion of nitric acid, five atoms of oxygen and one atom of 

 nitrogen, and in that of ammonia, three atoms of hydrogen 

 to one of nitrogen. The attainment of a knowledge of this 

 notation is easy, while the use of it is exceedingly convenient. 



Atomic volumes. — The spheres of repulsion of different 

 chemical atoms, or rather molecules, are probably different; 



