INTRODUCTION. ] 7 



Ink ; the theory of its formation is, that the astringent principl& 

 unites with the oxide of iron, and gum Arabic or sugar suspends the 

 precipitate. 



The burning of lime consists in the expulsion of the carbonic acid, 

 by heat ; the acid gas forms nearly one half of the weight of the 

 limestone, marble, and chalk. 



Art and science mutually aid each other, because art furnishes 

 hands and science eyes ; science without art is inefficient ; art with- 

 out science is blind. 



The philosophical chemist must understand the principles of the 

 chemical arts, and the more of the practice he knows the better. 



Chemical artists should understand the science, at least of their own 

 arts, and practical knowledge is of- course indispensable. 



Not satisfied with the knowledge of the external properties and the 

 mechanical relations, which are unfolded by Natural History and by 

 Physics, but taking them into view, and retaining and using their 

 principal discoveries, chemistry proceeds to investigate the hidden 

 constitution of every species of material existence, in earth, sea and 

 air. 



Earth, air, fire and water, were the four elements of the ancient 

 school. They have however, yielded to analysis, and water, bland 

 and simple as it seems, contains two bodies, whose properties, are en- 

 tirely different from its own and from those of each other ; burning, 

 when mingled and ignited in large quantities, with violent explo- 

 sion ; and in a small stream, with a heat, which melts and dissipates 

 the firmest substances. We should never have conjectured that 

 water, whose great prerogative it is, to extinguish fire, contains 

 both a combustible and a supporter of combustion. 



The air, the pabulum of life to the whole animal and vegetable 

 creation, mild and negative like water, is not simple but contains inci- 

 dentally many bodies, essentially however only two ; one of which 

 and that, constituting four fifths of the whole, is, and was intended to 

 be, in a high degree noxious and even deadly to animal life and fatal 

 to combustion. The air does not destroy life instead of invigorating 

 our frames, and extinguish instead of inflaming combustion, because 

 the prevalent noxious principle of the air (nitrogen) is balanced by a 

 life and fire-sustaining principle (oxygen) too vigorous to be trusted 

 alone, and therefore, diluted exactly to the proper degree, by the op- 

 posite principle, both being, by another extraordinary provision, sus- 

 tained, in constant proportion, and thus producing a salubrious and 

 unchanging atmosphere. 



The earth, under our feet, the soil, the sand, the gravel, the firm 

 substance of the rocks, is not simple. In this ancient but assumed 

 element, we have a double complexness. The one imagined, simple 



