XXX.] CLASSIFICATION. 675 



Perhaps it will he found in the sequel, that classification 

 is not only the beginning, but the culmination and the end, 

 of human knowledge." 



Classification Involving Ind^iction. 



The purpose of classification is the detection of the laws 

 of nature. However much the process may in some cases 

 be disguised, classification is not really distinct from the 

 process of perfect induction, wliereby we endeavour to 

 ascertain the connexions existing between properties of the 

 objects under treatment. There can be no use in placing 

 an object in a class unless something more than the fact 

 of being in the class is implied. If we arbitrarily formed 

 a class of metals and placed therein a selection from tlie 

 list of known metals made by ballot, we should have no 

 I'easou to expect that the rnetals in question would resemble 

 each other i-n. any points except that they are metals, and 

 have been selected by tlie ballot. Ikit when chemists 

 select from the list the five metals, potassium, sodium, 

 ciesium, rubidium, and lithium and call them the Alkaline 

 metals, a great deal is implied in this classification. On 

 comparing the qualities of these substances they are all 

 found to combine very energetically with oxygen, to decom- 

 ]jose water at all temperatures, and to form strongly basic 

 oxides, which aie highly soluble in water, yielding power- 

 fully caustic and alkaline hydrates from wliich water cannot 

 be e.\ ladled by heat. Their cai'bonates are also soluble in 

 water, and each metal forms only one chloride. It n)ay also 

 l>e expected that each salt of one of the metals will correspond 

 to a salt (jf each other metal, there being a general auiiloav 

 ijctween the compounds of these metals and their properties. 



Now in forming this class of alkaline metals, we have 

 done UKu-e than merely select a convenient order of 

 statement. We have arrived at a discovery of certain 

 empirical laws of nature, the ])robability being very con- 

 sitlerabh; that a metal which exhibits some of the pro]jerLies 

 (if alkaline metals will ulso possess the others. If we 

 discovered another metal whose carbonate was soluble in 

 water, and v/hich energetically coml)ined with water at all 

 temperatures, producing a strongly Inisic oxide, wc should 

 iuler that it would lurm uidy a single chloride, and that 



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