238 MEMOIR OF DR. DALTON, AND 



results he arrived at, and the process. 1st. By long reflection 

 on the constitution of bodies, especially of gases, he became 

 convinced of the necessity for ultimate particles, divisible or 

 not so. These particles unite together, and form of course a 

 definite compound. If the smallest part is definite, so is the 

 largest. This is the fundamental law of definite compounds. 

 2nd. Various numbers of atoms may unite — there may be 

 one, two, three, or more — there can be no division of atoms. 

 As large bulks are constituted just as small are, so multiple 

 proportion becomes a law by which bodies are constituted. 

 3rd. Compound bodies constituted as the above unite par- 

 ticle to particle in a manner exactly similar to simple 

 bodies, and so we have compound proportion, and are led to 

 a mode of inquiry into, and a method of expressing the most 

 complicated bodies. 4 th. If we obtain the relative weights of 

 the constituents of bodies we obtain the relative weights of the 

 atoms, because the smallest parts must be constituted as the 

 largest. 5th. The relative weights of the atoms become con- 

 stant expressions for the proportions of combinations. 



These are the fundamental principles which made chemistry 

 a science and hold it together, and although Dalton had no 

 direct help in discovering any of them, we have seen that 

 Higgins had already expressed the first two. Richter and 

 Fischer had made out numbers representing the reciprocal 

 proportion of bodies, and although not going to first princi- 

 ples, and establishing no law, Fischer's numbers adopted by 

 Richter, I believe in 1803, are really atomic weights or 

 equivalents, although they did not see them to be such. 



There existed, therefore, in the world material for com- 

 pleting the theory of combination, but there was no one who 

 saw it clearly, and no one who knew both parts published. 

 Dalton cannot be blamed for not knowing them ; no one knew 

 them. Although Dalton had to begin without their aid, the 

 custom of the world is to give credit to him who adds to its 

 accumulated knowledge, not to him who obtains knowledge in 



