274- On the Development of Electricity hy Pressure. 



In considering the manner in which the development of 

 electricity increases in bodies by the augmentation of pressure, 

 ought we not to refer to this cause certain luminous phaeno- 

 mena, the origin of which is as yet imperfectly known ? It is 

 said, for instance, that in the polar seas it often happens that 

 light is elicited by the shock of blocks of ice. These enor- 

 mous masses come in contact with a considerable quantity of 

 motion ; they must therefore experience great compression, 

 which induces upon each of them two different electric states. 

 At the moment when compression ceases, the two fluids im- 

 mediately recombine on account of the conductibility of the 

 ice. Is not the light disengaged to be attributed to the sud- 

 den recomposition of these fluids ? 



Iron struck with repeated blows also becomes luminous : 

 are not the same electric phaenomena of pressure produced in 

 this instance, as when two masses of ice are dashed together ? 



Summaiy. 

 In reviewing what we have just laid before our readers, it will be seen, 

 1° that all bodies acquii'e two different electric states by pressure ; — that 

 in two bodies, perfect conductors, this state of equilibrium ceases at the 

 moment in which the pressure is withdrawn ,• whereas when one of the 

 bodies is not a good conductor, the effect of the pressure continues for a 

 longer or shorter duration of time; — that pressure alone preserves the 

 equilibrium of the two fluids placed upon each of the surfaces ; since, when 

 there is any diminution of the pressure, and at the end of a certain time 

 the bodies are withdrawn from compression, neither of them retains more 

 than the quantity of electricity due to the remaining pressure ; — that ca- 

 loric modifies the development of electricity in a manner perfectly peculiar 

 to itself, — that the electric intensity increases at first in the direct ratio of 

 the pressure, and that it is probable that this relation diminishes in high 

 pressures, in the same degree as bodies lose their compressibility : — lastly, 

 we have seen, that it is probable that the light disengaged in great shocks 

 is owing to the sudden recomposition of the two fluids, which had been 

 developed upon each surface at the moment of compression. 



LIV. Afeta Observations on the Natural Distrihition of ani- 

 mated Nature. By A Fellow of the Linnean Society. 



[Continued from p. 202.] 

 TJT ERE WITH I send you a continuation of my tabular 

 -*■-■• distribution of Nature, containing the Animal Kingdom: 

 but it is given with diffidence, and rather with a view to excite 

 examination, than with a due conviction of any real service it 

 is capable of affording even to a naturalist ; and by such a 

 reader only will it be easily comprehended. Yours, &c. 



October 1823. F.L.S. 



Erratum. — In the printed table inserted in your last Number, the 

 words Dicotyledonous and Monocotyledonous have been transposed, owing 

 to a mistake in transcribing. It is necessary that the reader should correct 

 this, as the error it gives ris* to is very important. 



Natural 



