78 - Scientific Newt, Accounts of Books^ &c. 



of the ftream, as it pafled out at the lateral orifice, was evident to the eye ; although, from 

 various circumftances, the quantity and direftion of its motion could not be fubje£ted to 

 exa6l menfuration. This fpecies of fonorous cavity feems fufceptible of but few harmonic 

 founds. It wasobferved, that a faint blaft produced a much greater frequency of vibrations 

 than that which was appropriate to the c^Vity : a circumftance fimilar to this obtains alfo in 

 large organ pipes ; but, feveral minute obfervations of this kind, although they might affift 

 in forming a theory of the origin of vibrations, or in confirming fuch a theory drawn from 

 other fources, yet, as ^hey are not alone fufficient to afford any general conclufions, are 

 omitted at prefent, for the fake of brevity. 



fTe be continued.) 



SCIENTIFIC NEWS, ACCOUNTS OF BOOKS, ^e. 



Galvanic Pile cotijijling of one and the fame Metal throughout. 



M. 



LR. Humphry Davy, who is at prefent attached to the Royal Inftitution, has difco- 

 vered, that the difference of the metals is not efTential to the efFeft produced in the pile of 

 Volta. From his former reafoning on thefe important phenomena, (fee our Journal IV. 

 380, 394) he was led to make trial of powers by which that difference of oxydation at 

 the furfaces, which appears to be efTential to the efFeft, and has hitherto arifen from the 

 habitudes of the metals themfelves, might be'produced with fimilar confequences by chang- 

 ing the folvents. The metals hitherto tried each to form a pile by itfelf, and as far as my 

 recoUeftion ferves are filver, copper, zinc, and lead ; and one of the arrangements of the 

 chemical agents is thus ; a plate of metal, cloth foaked in diluted nitrous acid, cloth foaked 

 in water, cloth foaked in fulphuret of pot-afh ; then another plate of the fame metal, and 

 the three cloths as before : in which manner the repe'titions may be continued at pleafure. 

 If a trough be ufed with cells, and the feparation between the acid and the fulphuret of 

 pot-afh be made by a plate of horn inflead of the cloth imbibed with water, the two fluids 

 may be connefted by a flip of wetted cloth hung over the upper edge of the horn. This 

 will complete the communication without occafioning any mixture, becaufe water is lighter 

 than either of the other fluids. It is remarkable that the efFe£ls of this pile are the reverfe 

 of what happens when the difference of adion depends on the metals ; that is to fay, the 

 extrication of hydrogen in the tube of communication, is made from the oppofite wire to 

 that from which it would have been made with the common pile. 



Among the refledions and conclufions to which this valuable experiment muft give rife, 

 it is not one of the leaft important, that it overthrows the theory of the learned inventor 

 Volta, who confiders the current of eleftricity as being produced by the difference of con- 

 ducing power in the different metals. And in this obfcure region of refearch, though we 

 are altogether unacquainted with the power by which the eleftricity is accumulated, it is 

 one ftep towards a true theory to have afcertained, that one of thofe already offtred is 



without foundation. 



Philofophical 



