1820.] Dr. Macneven on the Atomic Tkeory. 195 



Article VI. 



Exposition of the Atomic Theory of Chemistry ; and the Doctrine 

 of Definite Proportions. By William James Macneven, M.D. 

 Professor of Chemistry and Materia Medica in the College of 

 Physicians and Surgeons of the University of the State of 

 New- York. 



1. It has been know^n, ever since chemists acquired the art 

 of analyzing bodies, that substances always enter into chemical 

 combination in determinate proportions. Nitrate of potash^ 

 under all circumstances and in all situations, consists invariably 

 of 64 parts nitric acid and 46 potash, per cent. Common salt of 

 46 muriatic acid and 54 soda ; no matter whether the salt was 

 taken from the sea, or from a spring, or artificially made, these 

 proportions of the constituent parts are uniform. Carbonate of 

 lime is always found to consist of 43-2 carbonic acid and 56*8 

 lime. Sulphate of barytes of 34-5 sulphuric acid and 65-5 

 barytes. The more rigorously this law has been examined byi 

 accurate analysis, the more conspicuous and decided have 

 become the proofs of its reality. It is, therefore, universally 

 admitted ; indeed, it is obvious, that if there was not a law of 

 nature to determine and preserve these fixed proportions, there 

 could be no uniformity in compound bodies : but the uniformity 

 and fixedness of the law necessarily depend on some ulterior 

 cause which renders all other combinations impossible. Now, 

 this cause, whatever it be, must constitute the principal basis of 

 chemical philosophy, and well understood and rigidly applied, it 

 would introduce mathematical precision into our chemical reason- 

 ings and conclusions. In ascending to the cause we can assiga 

 it no other residence than those elementary particles of matter, 

 which are so constituted as to be exempt from decay or change, 

 though they are capable of being variously compounded toge- 

 ther and separated again, so as to give origin to the perpetual 

 transitions of elementary into organized matter ; but the nature 

 of the elements themselves is immutable ; the forms only can 

 vary. The indefatigable alchymist frequently exhausted every 

 device and process, endeavouring, with keen research and pro- 

 digal talent, to alter the nature of matter, and transmute one 

 species of metal into another, but he was eternally foiled in this 

 chimerical attempt. 



The productions of nature have not only succeeded one ano- 

 ther in the same general order, but have been from the begin-. 

 ning invariably the same. An oak of the present time has the 

 same general nature and the same properties as those of all other 

 oaks that ever existed ; we find the same texture in its wood 

 and bark; a similar disposition in general in its root and 

 branches ; the leaves have the same form ; the juices the same 



n2 



