Dr. Agassiz on the Classification of Fish. 459 



chemical action at one pair of plates cannot pass by another pair ex- 

 cept an equal chemical action take place there ; and as the chemical 

 and electrical action are always equivalent, the equal chemical action 

 at the second pair will do no more than suffice to transfer forwards the 

 forces disturbed at the first pair, and can add nothing to their quan- 

 tity : but they can add to their intensity, and in fact the recurrence 

 of a second chemical action at the second pair of plates has exactly 

 the same effect as would be produced by a more intense chemical ac- 

 tion at the first pair. In this way it is that numbers of plates give 

 energy to the voltaic pile, and enable its power to penetrate elec- 

 trolytic bodies and permeate bad conductors in a manner which could 

 not be done by the electricity of a few pairs of plates only. 



The fourth part of the paper relates to the resistance opposed to 

 the electric current at the place of decomposition, and refers this at 

 once to the resistance of the chemical affinity which has to be over- 

 come. This of course varies with the number of places where de- 

 composition is effected, the strength of the affinity of the elements of 

 the decomposing body for each other, and the nature of the substance 

 against which the decomposition is effected, and by which it may very 

 frequently be assisted. All these are taken into account, their ge- 

 neral, and occasionally particular, results shown, and their perfect 

 harmony with the principles previously advanced pointed out. 



In the last part of the paper some general remarks on the active 

 voltaic battery are made, in which the influence of several distinct 

 causes in producing a rapid change and deterioration of action is 

 pointed out. Each of these causes is considered separately, and the 

 effects they produce are shown to be necessary consequences of the 

 principles already laid down as those of the voltaic battery. 



GEOLOGICAL SOCIETY. 



Nov. 5, 1834?. — The Society assembled this evening for the Session. 

 A paper was read " On a new Classification of Fishes, and on the Geo- 

 logical Distribution of Fossil Fishes," by Prof. Agassiz, of Neuchatel. 



The author begins by stating that the state of the science of Ich- 

 thyology had obliged him to undertake an examination of recent 

 fish for the sake of comparing them with the fossil species, and in 

 doing so he had arrived at a classification offish, in general, differing 

 considerably from the various arrangements previously adopted by- 

 naturalists. One of the essential characters of fish is, to have their 

 skin covered with scales of a peculiar form and structure. This co- 

 vering, which protects the animal without, is in direct relation with 

 its internal organization, and Dr. Agassiz has found that by an at- 

 tentive examination of the scales, fish may be divided into more na- 

 tural orders than had hitherto been established. In this manner he 

 has established four orders, which bear some relation to the divisions 

 of Artedi and Cuvier, but one of which, hitherto completely misun- 

 derstood, is almost exclusively composed of genera whose species 

 are only found in the most ancient strata in the crust of our globe. 

 These four orders are, the Placoidians, which comprehend the car- 

 tilaginous fish of Cuvier, with the exception of the sturgeon j the 



3N2 



