ATTRACTION. 171 



weights of the atoms will be as those numbers ; but as it requires two 

 volumes of hydrogen gas to saturate one volume of oxygen gas, it 

 follows that if the two volumes of hydrogen be expressed by 1, viz. 

 be regarded as one atom, half a volume of oxygen must be the 

 equivalent of the hydrogen, arid will be expressed by 8.* 



(jjj>) Either of these elementsf being taken as unity, then the 

 weights of the atoms of other bodies may also be expressed by 

 numbers, having an arithmetical relation to those attached to these 

 two elements, and thus we may construct a table of atomic weights. 



(kkk.) If we could be certain that we actually know the lowest pro- 

 portions in which bodies combine, and that in them the constituents 

 are united atom and atom, then their definite proportions and their 

 atomic weights would correspond ; or at least they would be multiples 

 and divisors, generally, of each other, and always by whole numbers. 



(III.) But we can never be certain, that we either know the small- 

 est combining quantities of bodies, or that those quantities, if known, 

 are relatively in the proportion of atom and atom, or of one atom of 

 one and of two of another, or vice versa, or of some other pro- 

 portion ; we cannot therefore be certain that our atomic hypothesis is 

 true. 



(mmm.) This however does not affect the truth of the theory of 

 multiple proportions ; that great discovery is independent of hypothe- 

 sis, because the exactness and arithmetical relation of the proportions 

 is a matter of fact, and will still be true, whether the lowest combin- 

 ation is formed by atom and atom of different bodies, or by one atom 

 of one and two of another, or the reverse ; or by any other assort- 

 ment that may be imagined. 



(nnn.) The atomic theory is an elegant hypothesis, framed to ac- 

 count for definite and multiple proportions, and may be either true 

 or false without affecting that sublime truth, which deserves to be in- 

 scribed on the same tablet with the laws of gravitation and projection. 



(ooo.) Still the hypothesis is highly probable, and the probability 

 of its truth is much increased by its surprising coincidence with 

 facts. 



(ppp-) No student in chemistry, should however, imagine that the 

 doctrine of definite and multiple proportions must stand or fall with 

 the atomic theory. The latter may be discarded, without in the least 

 affecting the former ; but the truth of the former is indispensable to 

 the existence of the latter. 



I shall, as much as possible, avoid the use of the word atom, since we 

 have no positive knowledge of the nature, forms, number and weight 

 of the atoms of any thing ; as the word is short, it may however 



* See Mr. Finch's paper on the atomic theory, Am. Jour. Vol. XIV, p. 24. 

 t Other elements might have been used for this purpose ; but none are equally 

 oxygen and hydrogen. 



