232 Intelligence and Miscellaneous Articles. 



sitiveness of the observation is considerably augmented, and the 

 determination is made with much greater precision than the ordi- 

 nary measurements. 



On discussing the perturbing influence of a small difference be- 

 tween the real position of the plane of symmetry of the polarizer 

 and the initial position of the principal plaue of the analyzer, one 

 perceives that the error committed in the orientation of the axis of 

 the crystal plate is about one half less, and that, if all the vie wings 

 are made with the same precision, the employment of the foregoing 

 method reduces the errors of observation to about three fourths of 

 their ralue for the double, and to two thirds for the triple deflec- 

 tions. 



Besides, the observer finds in the different determinations a very 

 precious mutual control, permitting him to fix the value of the ap- 

 proximation which the numbers obtained permit. 



The foregoing considerations have induced me to lay before the 

 Academy this new method, which permits one, by the mere inter- 

 position of a suitably chosen crystal plate, to augment the precision 

 of the measurements respecting various phenomena of rotatory 

 polarization, the observation of which is sometimes an extremely 

 delicate process. — Comptes Rendus de VAcademiedes Sciences, July 18, 

 1881, t.xciii. pp. 143-145. 



CHANGE OF STATE : SOLID-LIQUID. 



To the Editors of the Philosophical Magazine and Journal. 



Mason College, Birmingham, 

 GrENTLEMEN, August 4, 1881. 



In a paper on the Change from the Solid to the Liquid State, 

 which appeared in the July number of the Philosophical Magazine, 

 I described some experiments on the temperature of melting ice 

 when the ice is under much greater pressure than the water in con- 

 tact with it. In these experiments I thought I had obtained some 

 confirmation of the preceding theory, that the melting-point would 

 be lowered much more than when both ice and water are submitted 

 to the same per s sure. 



I have lately repeated the experiments more fully ; but I do not 

 find my previous results confirmed. I can only suppose that they 

 were wrong, and that the error arose from insufficient precautions 

 as to the temperature of the thermopile- junction which Mas placed 

 in melting ice. I now find that the water freezes in the pores of 

 the sand around the junction placed under the compressed ice. As, 

 therefore, the conditions necessary to success are not realized, there 

 is no reason to expect any lowering beyond that which takes place 

 when both ice and water are submitted to the same pressure. 



I regret that the hasty publication of my previous experiments 

 should render it necessary for me to ask you to publish this expla- 

 nation. 



I remain, G-entlemen, 



Tours faithfully, 



J. H. PoYNTING. 



