124 ^n Address to Chemists. [Fjjb. 



gas ? If there be, the notion may be considered as an interesting 

 conjecture ; but if there be no such fact, the notion is a mere 

 dream. There can be no doubt that if we give free liberty to our 

 imagination in this manner, the science will degenerate into a mass 

 of vain speculations, of no utility whatever, because founded on 

 nothing but imagination. My idea, that in every inorganic com- 

 bination one of the elements enters as unity, is founded on the 

 circumstance that in all the inorganic bodies which I have analyzed, 

 and I have analyzed a great number, I have found it to be so. 

 Besides, if this were not the case, it is evident that all traces of 

 chemical proportions would disappear in combinations which consist 

 of various oxides, and could only be perceived in the most simple 

 combinations, I have then founded my opinion on experience. Can 

 Mr. Dalton produce an instance in which this opinion is obviously 

 inaccurate ? 



Mr. Dalton then proceeds to remove the difficulties which I 

 found attached to the corpuscular theory. I shall pass by the first, 

 which he finds that I myself have obviated in a manner conformable 

 to his opinion. The second difficulty consists in this— I iiave found 

 compounds which are represented, for example, by A O^ + li BO, 

 which is contrary to the views of the atomic theory ; while a com- 

 bination of A O^ + B O- does not exist, although it be con- 

 formable to that theory. Mr. Dalton removes the first part of these 

 difficulties, by saying,' " the body B in such a case has in reality 

 three atoms of oxygen for one of metal, and the union in question 

 is 2 A O^ + B O'." 1 have given two examples of which Mr. 

 Dalton has said nothing. These examples are the subarseniate of 

 lead (As O^ + 1^ P O")' ^"^^ ^^^ subsulphate of copper (S O^ + 

 \4r Cu 0-). It is evident that neither of these examples admits the 

 explanation by which Mr. Dalton has endeavoured to remove the 

 difficulty ; for neither the oxide of lead nor copper can contain 

 three atoms of oxygen, Mr. Dalton adds merely, that he considers 

 with Proust, minium as a compound of yellow oxide and brown 

 oxide of lead ; from which it seems to follow that he considers the 

 subarseniate of lead as As O^ + 3 P O. But what reason has Mr. 

 Dalton to consider minium as composed in this manner? The 

 necessity of it for his theory ? But this necessity proves nothing as 

 lon'T as the theory itself is sub judice, which it probably will be for 

 a long time to come. We may likewise explain the subsulphate of 

 copper by supposing sulphuric acid composed of S + G O, or black 

 oxide of copper Cu -f O, and of course the protoxide 2 Cu -f O. 

 But here lies the difficulty; for we have other reasons for consider- 

 ing the acid as S -f 3 O, and the oxide Cu + 2 O. These diffi- 

 culties cannot be removed b; a stroke of the pen. Yet I am per- 

 suaded that both myself sind Mr. Dalton will in time make use of 

 tiiese very difficulties to determine the true number of atoms in 

 such and such compound bodies ; but we must in the first place 

 make a much greater number of experiments on these subjects than 

 we possess at present ; for it is not spepulation alone, but experi- 



