184 Miscellamous Intelligence. 



an immense number of points in the same pair are acted on at 

 once by the fluid ; hence rapid and considerable disengagement 

 of electro-caloric which is immediately urged forward by the 

 electro-motive force, and conveyed by the conductors. These 

 large plates without being numerous, ought to produce a great 

 calorific effect, because each voltaic element or pair, produces 

 in a tempuscule given, a quantity of electro-caloric at least pro- 

 portionate to its surface, and perhaps even in a higher ratio. 



It is not the same with the apparatus of many small plates. 

 The quantity of electro-caloric disengaged in the tempuscule 

 given, being proportionate to the surface of the plates will be 

 inconsiderable, because of the smallness of that surface. It is 

 urged forward by the electro-motive force at the instant of its 

 production, and it traverses the series of elements without ever 

 becoming considerable,- because the initial disengagement was 

 small, and cooling would diminish its quantity whilst passing 

 the numerous metallic communications from one couple to 

 another. 



On the other hand, this apparatus will be far more effectual 

 in producing chemical decompositions than the other, because 

 the chemical action is probably dependant on the electro-motive 

 action, and it increases with it, and this in a given interval of 

 time ; it is much more frequent, and consequently more produc- 

 tive in an apparatus with many plates than in one with few : thus, 

 for instance, suppose 100 of the electro-motive and decomposing 

 vibrations in a second of time, an apparatus with six pair of 

 large plates would only produce 600 of these active vibrations 

 in a second, whilst an apparatus with 500 pair of small plates 

 would produce 500 x 100 =: 50,000 similar vibrations in the 

 same time. 



It may be also that the extreme abundance, and so to speak, 

 violence of the electro-caloric current in the apparatus with 

 large plates, injures its chemical effect by the mechanical im- 

 pulsion which the current exerts on its entrance into the fluid 

 to be decomposed ; whilst in the many small plated apparatus, 

 the current of electro-caloric being less powerful, and the vibra- 

 tions more numerous, the polar decomposing effect is more 

 energetic. 



These ihoughts, M. Pictet judiciously adds, are merely given 

 as conjectures ! they wait the result of experiments, to be either 

 confirmed or rejected. — Bib. Univer. xvi. p. 293. 



17, Electro-Magnetic Instruments invented hy M. de la Rive. 

 —Two excellent little instruments have been invented by M. 

 de la Rive, of Geneva, to illustrate the various phenomena of 

 electro-magnetism, with very little trouble, and at a very tri- 

 fling expense. The first consists of a small voltaic combination 

 attached to a cork ; the plate of zinc is nearly half an inch wide, 

 and extends about an inch and a half below the cork, its 



