.1820.] the Atomic Theory. 199 



theory. He delivered the composition of sulphurous and sulphu- 

 ric acids, the composition of water and the compounds of 

 oxyo-en and nitrogen nearly as they are now received. But his 

 own experiments were too few, and there were not data enough 

 furnished by others to supply sufficient materials for the construc- 

 tion of the atomic theoVy. During the 21 years that elapsed 

 between the publication of the comparative view of Mr. Higgins 

 and the elements of chemical philosophy by Dalton, with more 

 industry, the former might, perhaps, have secured to hiinselt the 

 reputation for which he is now so solicitous ; but, if liberal and 

 candid, he will confess that celebrity without labour is neither 

 leo-itimate nor attainable in the walks of science, and that the 

 fame of a discovery belongs rightfully to him, who is not only 

 the most sedulous, but also the first to promulgate and apply it. 

 Without being the discoverer of the atomic theory, no man in 

 Britain has done so much for it as Dr. Thomson ; and by Berze- 

 lius and Gay-Lussac its principles have been carried as much 

 beyond where Dalton left them, as he exceeded the scanty sug- 

 gestions furnished by Mr. Higgins. It is now every where 

 received, and constantly improving. 



7. The invariable permanency of chemical compounds cannot 

 be owing to any thing else than the union of a certain determi- 

 nate number of the atoms of one constituent with a certain 

 determinate number of the atoms of the other. The proof ot this 

 position will be more easy and striking, if we first take an 

 example from the union of gaseous bodies, the atoms of which, 

 unrestrained by the force of cohesion, are at liberty to arrange 

 themselves according to their chemical affinities. 



Let the compound to be investigated be water, which is known 

 to result from the condensation of oxygen and hydrogen gases 

 when they are ignited together. We shall denote the atoms of 

 oxygen which unite by x, and those of hydrogen by y, and then 

 an integrant particle of water will, in every case, be x + y. 



The numbers x and y are easily found by making an accurate 

 analysis of the different compounds into which various propor- 

 tions of oxygen and hydrogen enter. Let us take water. It is 

 known from experiment that 100 cubic inches of oxygen gas, 

 weigh 33-888 grs. and that 100 cubic inches of hydrogen weigh 

 2-117 o-rs. If these volumes be mixed together and the electric 

 spark passed through them, there will be a condensation of all 

 the hydrogen and half the oxygen ; so that 100 cubic inches, or 

 2-117 grs. of hydrogen can condense no more than 60 cubic 

 inches, or 16-944 grs. of oxygen. But, if we mix 2 volumes of 

 hydrogen, or 4-234 grs. wfth 1 of oxygen, and then pass the 

 electric spark, there will be a complete condensation of both 

 the gases, and a portion of water left, precisely equal to their 

 joint weights ; consequently the weight of oxygen in water is to 

 the weight of ■ hydrogen in water, as 16-944 is to 2d 17, or as 

 33-888 to 4-234, aU which, reduced to their lowest teinis, are as 



