380 Analysis of Scientific Books. 



previously demonstrated by Mr. Children in the niagnificcntscries 

 df experiments which he instituted at Tunbridge with batteries 

 of large plates, and of which an account is given in the Philoso- 

 phical Transactions for the years 1809 and 1815*, and he in- 

 geniously referred this variation of heat to the variable resist- 

 ance opposed to the passage of electricity, assuming the eleva- 

 tion of temperature to be inversely proportionate to the conduct- 

 ing power. " The greatest heat, however," says Sir H. Davy, 

 " is produced in air, where there is reason to suppose the least 

 resistance, and as the presence of heat renders bodies v?orse 

 conductors, another view may be taken ; namely, that the ex- 

 citation of heat occasions the imperfection of the conducting 

 power. But till the causes of heat and of electricity are known, 

 and of that peculiar constitution of matter which excites the 

 one, and transmits or propagates the other, our reasoning on 

 this subject must be inconclusive." 



This is the concluding paper of the Philosophical Transac- 

 tions for the year 1821. The hasty sketch of its contents in 

 this and in our preceding Number will enable our readers to 

 appreciate the novelty and importance of the papers printed in 

 this volume ; and will serve, we hope, as an index of reference 

 to its valuable and multifarious information. 



In taking our leave of this publication we seize the opportu- 

 nity which it suggests of congratulating the members of the 

 Royal Society upon the dignified independence and exalted sta- 

 tion to which that learned body has attained, and which it pro- 

 mises to preserve with untarnished and even increasing splen- 

 dour. 



* The facility with which an important discovery may escape the most 

 vigilant observers is brought to our recollection by the multiplied attempts 

 that were made during these experiments to influence the magnetic needle by 

 the voltaic pile : they failed, because the separate poles only were presented 

 to it : had the needle been at hand when the bar of platinum of 2^ inches 

 length, and -V^ inch diameter, was ignited by this powerful apparatus, the 

 whole of the phenomena might have been developed, and under circum- 

 stances most favourable to their investigation. 



