344 Miscellanies. 



The main object proposed is, to present the science of Chemistry, in 

 an intelligible form, to those who are learning its elements. The 

 attempt has been made, to unite copiousness with brevity and perspi- 

 cuity ; and to arrange the subordinate parts consistently with a gene- 

 ral unity of design. That it may prove the more valuable and inter- 

 esting, to those for whom it is written, the leading uses of the various 

 substances are particularly mentioned ; practical applications are 

 interwoven with scientific principles, and many miscellaneous facts, 

 not always indispensable to the text, are preserved in the notes. 



The book was written, not to advance the knowledge of masters 

 in the science, but to aid the progress of learners ; and it is obvious 

 that such an arrangement as might be most acceptable to the former, 

 might be inexpedient for the latter, to whom at the outset, the whole 

 is a ter7'a incognita. None but those who have been concerned in 

 teaching, can duly appreciate the difficulty of finding our way into 

 the mind of the youthful pupil, and of fixing there the knowledge 

 that we present to him. In the very commencement of his studies, 

 he cannot be an adequate judge of our theoretical views, with re- 

 gard to classification and arrangement ; he may even fail to under- 

 stand us, when we discuss them, and he will be most profited, and 

 best satisfied, by that arrangement, which, in the most interesting and 

 intelligible manner, presents to him the greatest amount of useful 

 knowledge. In courses of instruction, and in books to accompany 

 them, this object should, therefore, be paramount to every other. 



With respect to arrangement, there are, however, certain points, 

 in which most writers on Chemistry, and most teachers of the science 

 agree. In general, the great powers that produce and influence 

 chemical phenomena, namely, Heat, Light, Electricity, and Attrac- 

 tion, are first introduced ; and their agency is illustrated through the 

 whole chemical history of matter. 



In arranging the simple bodies, all agree to place oxygen first, and 

 the metals last. The remaining elementary bodies are usually em- 

 ployed to fill the hiatus which lies between them. They are the 

 sirnple combustibles, and those agents, which, in chemical and elec- 

 trical powers, are closely allied to oxygen, namely, chlorinej iodine 

 and bromine.* 



^ Fluorine is not lueiifioncd, because its very existence is doubtful. 



