Mr R. Adie's Account of Electrical Experiments. 327 



finite variety of nature — each genus, each, family has its cha- 

 racteristic features, and its specific variations occur within 

 fixed limits. In one family the absence of a central crest of 

 the cranium may constitute a characteristic feature common to 

 the Avhole family, while in another this crest will form but a 

 generic or specific character, and so on. To arrive at an exact 

 and minute knowledge of the laws which determine all the 

 variations that may occur in the species, genera, and families, 

 it will be necessary to possess the crania of all fish hitherto 

 known. Let us hope that some day we shall arrive at this 

 point ; at present we are still far distant from it. 



To give a sketch of the manner in which the osteology of 

 fish must be treated for the purpose of throwing light on the 

 investigation of fossil fish, and, in particular, on those of Shep- 

 pey, I shall indicate, in a few words, the characteristic features 

 of the principal families, representatives of which have been 

 met with in the London clay. If I pass over in silence the 

 other families, it is not that I have neglected them ; but, not 

 wishing to extend this report to too great a length, I shall 

 confine myself exclusively to those which have representatives 

 among the fossils of Sheppey. 



CTo be concluded in our next Number. J 



An Account of Electrical Experiments. By Mr R. Adie, 

 Liverpool. Communicated by the Author. 



In the 75th Number of this Journal, I gave the details of some 

 experiments which were designed to prove water batteries, to sustain 

 their action by absorbing oxygen from the air. The present expe- 

 riments are submitted as a continuation of the former, in order to 

 determine the limits of the oxygen absorbing galvanic couples, and 

 shew where they pass into those that disunite the elements of water, 

 and act independent of the atmosphere ; also to shew that in an 

 oxygen absorbing couple, the gas is taken up around the negative 

 plate. And to prove that the sectional area of the fluid in the cell 

 of a battery governs the quantity of electricity lost through the re- 

 sistance to conduction of the electrical current in passing from plate 

 to plate ; so that, where the wet materials of the earth form the 

 battery cell, its infinitely great sectional area, render changes of 

 distance betwixt the plates incapable of eflecting the quantity of 

 electricity conducted. 



A zinc and platina couple, connected in the usual manner with 



