CHEMISTRY. 



ing effects from each other, the opera- 

 tion of the mind is distinguished by the 

 same name ; but when, from the general 

 results, we show in what manner particu- 

 lar events are produced by combining 

 bodies together, the method is distin- 

 guished by the term synthesis. 



The synthetical method of teaching is 

 undoubtedly the most luminous and 

 clear, where the first principles or simple 

 elements of our knowledge are known 

 or admitted, as is the case in geometry. 

 But in chemistry this method of teaching 

 cannot, from our imperfect knowledge 

 of the facts, be generally adopted, with- 

 out admitting the simplicity of a variety 

 of substances, concerning which there is 

 just reason to doubt. 



It is true, indeed, that such admissions 

 are generally made with a previous notice 

 or reservation of this uncertainty. But 

 by the constant use of the supposed facts, 

 along with others which are better estab- 

 lished, the mind becomes habituated to 

 mix hypothesis with facts ; and the ima- 

 ginary beauty of connected science must 

 from time to time be destroyed by the ap- 

 pearance of new truths. The revolutions 

 of chemical science have amply shown 

 this; and the numerous imperfections 

 which still remain, have left considerable 

 latitude for the arrange ment'of materials 

 in a system of chemistry. If the theory 

 were in its commencement, a treatise on 

 chemistry would be little more than a 

 collection of receipts for processes ; and 

 even in the present state of the science, 

 different authors of credit and respecta- 

 bility greatly differ in the disposal of 

 their subjects. Operative chemistry 

 usually precedes the theory in the ear- 

 lier works. Some writers treat of com- 

 pound bodies, and deduce their princi- 

 ples or component parts in the way of 

 analysis : while others begin with the 

 habitudes or powers by which the seve- 

 ral changes are effected. But it must be 

 confessed, nowithstanding the magni- 

 tude of the discoveries which have been 

 really made, and the elevated preten- 

 sions of a few theorists, that the practical 

 science is still in its infancy. Every one 

 of the phenomena is sufficiently compli- 

 cated as to be referrible to various topics 

 of consideration; and to which of these 

 in a general way our attention shall be 

 first directed, is in many cases a matter of 

 indifference. It appears to us that the 

 advantages of treating the subjects in a 

 popular way, by first attending to the 

 general properties and habitudes of bo- 

 dies, and the methods of operating upon 



them, and from thence proceeding to 

 the different classes of bodies, are such 

 as entitle this method to a preference 

 before other arrangements, which afford 

 a greater appearance of synthetical or- 

 der 



When we have simplified our notions 

 of the causes of change which happen to 

 bodies under the distinction or division 

 of chemistry, we must resolve them into 

 two, namely, heat and attraction. Daily 

 experience shows us that bodies may be 

 more or less heated, and also that they 

 adhere to each other. We are in truth 

 unable to proceed farther in our abstrac- 

 tions. The causes of those well known 

 effects have not yet been develoved by 

 the manifestation of any more simple 

 facts upon which they may depend. We 

 can only observe the laws, according to 

 which these powers have been found to 

 act, and make our classification of the 

 phenomena ; and as it is of some utility, 

 in directing our future researches, to 

 make conjectures by analogy, it may also 

 be permitted to speculate upon the 

 causes of these primary effects, provided 

 it be done with caution, and without that 

 bigotry, which even in systems of philo- 

 sophy has so frequently established the 

 results of error. 



Besides the effects of heat and attrac- 

 tion, we find that bodies are changed and 

 modified by light, electricity, galvanism, 

 and magnetism ; the three last of which 

 are accompanied by attraction, or repul- 

 sion. But as these are much less gene- 

 rally applicable in operative chemistry 

 than the powers first mentioned, and as 

 it seems likely that future discoveries 

 may lead to some intimate relation, or 

 perhaps show the identity of the cause 

 of heat, light, and the other affections of 

 matter, which have here engaged our at- 

 tention, it is unnecessary to enlarge upon 

 these in the present article. 



The word attraction denotes the unex- 

 plained tendency which bodies have to 

 move to each other. We observe it act- 

 ing at a distance in the fall of bodies on 

 the surface of the earth, and in the mo- 

 tions of the heavenly bodies, as well as in 

 such as are affected by electricity, gal- 

 vanism, er magnetism ; and in the cohe- 

 sion which gives solidity, or, more pro- 

 perly, rigidity, to bodies, as well as in 

 those effects wherein the parts of differ- 

 ent bodies unite to form new compounds, 

 we deduce its effects from motions or ac- 

 tions, which cannot be separately distin- 

 guished. And these differences, though 

 they cannot be shown to arise from one 



