210 MEMOIR OF DR. DALTON, AND 



subject, but it was expressed in clearer words, and still earlier, 

 by Higgins. This idea leads directly to the atomic theory and 

 theory of equivalents. Here it is not followed out. 



The sixth experience of first definition gives the theory 

 of reciprocal saturation, when double decomposition takes 

 place in solutions. This is the discovery which has been at- 

 tributed to Wenzel. Let us translate his formulas into the 

 present symbols by an example : — 



A^O NO5— NO5, NO5+KO SO3— SO3, SO3 

 ^NOg'+KO SO3— SOa+SOg+A^ONOs— NO5. 



He says the products of neutral salts are nearly without 

 exception neutral, but nevertheless sees enough to form a law. 

 Wenzel, with similar results, had not seen a law. 



He endeavours to shew the relative amount of force exerted 

 by different substances when decomposition takes place, 

 but he gets no farther than the fact that certain forces are 

 equal, some must be greater, and others must be less. 

 In this district of inquiry, an example of which may be 

 found in Theorem I., what appears to be the enunciation of 

 an important law, frequently turns out to be the mere expres- 

 sion of a common-place, giving no information to the chemist. 

 Such laws being in a certain sense universal, they are now 

 left out of chemical works, as the mind can readily draw the 

 conclusion for itself, if the opportunity offers. 



He then shews the method of obtaining the proportion of 

 the elements in a compound. This had been pursued with 

 great care by Wenzel. 



The great aim of Richter is not perceived in reciprocal 

 proportion, but in the attempt to make the combining 

 numbers of all bodies a series in arithmetical progression, and 

 so to bring number, quantity, and order into the arrangement 

 of the elements. In the series which he has formed, I think 

 we may say that he has failed to prove his point. The 

 numbers he had were too few, and the mode of obtaining the 

 order is by no means satisfactory. There is, however, a 



