504 Sir W. Snow Harris on the Correct Interpretation 



the elasticity of vapours*) is approximately true as applied to 

 this liquid. This law was found to apply, with nearly equal 

 exactness, to the results of all the experiments with diluted 

 acids. 



In the experiment with stong sulphuric acid, it was found that 

 at a pressure of 2 inches the corresponding temperature was 

 about 500°, and at the mean pressure of the atmosphere about 

 640°. But, owing to the exceedingly high temperatures employed 

 in this case, the temperature corresponding to any given pres- 

 sure could not be determined with much precision. 



Hastings, November 14, 1863. 



LXXII. On the Correct Interpretation of the Electrical Terms In- 

 tensity and Tension. By Sir W. Snow Harris, FM.S.f 



[With a Plate.] 



1. rTlHERE have been few scientific terms so indefinitely and 

 J- loosely employed in the sister sciences of electricity and 

 magnetism as the terms " intensity " and " tension." The elec- 

 trical term " quantity " is intelligible enough, and is understood 

 to designate the actual amount of the unknown agency, whatever it 

 be, constituting electrical force. The term " inteusity," however, 

 has been made to represent all sorts of hypothetical views of the 

 occult nature of electricity itself, often vague and unsatisfactory : 

 amongst others it has been made to signify an hypothetical elastic 

 quality, the electrical agency being supposed capable of changing 

 its state or condition — just as we may imagine a spring to have 

 greater or less elastic power. M. De la Rive observes, " Besides 

 the quantity of electricity, it is necessary to know its density/' 

 thereby inferring a greater or less degree of what may be termed 

 solidification or compactness of particles, and assuming the elec- 

 trical agency liable to compression or expansion. " La densite," 

 he observes, " peut etre determinee directement au moyen d'un 

 electrometre a poids," that is to say, by an intensity-electrometer. 

 Again, Riess, as also M. De la Rive, infers that in distributing 

 a given quantity of electricity over three or four jars instead of 

 one jar, its density or elastic force is thereby diminished, and a 

 change effected in the quality of the electric agency; they are 

 hence led to represent this hypothetical change by the expression 



* At equal distances from the boiling temperatures the elasticities of the 

 vapours of different liquids are for the most part nearly equal. This law 

 has been found to be approximately true for the vapours of water, alcohol, 

 ether, and sulphide of carbon. 



t Communicated by the Author. 



