436 Proceedings of the British Association. 



water when liquefied. — Some remarks were then made by Mr. Pearsall, 

 on the action of hydrogen on platina. An experiment was named by 

 Mr. Harcourt, in which a platina tube was destroyed by an attempt to 

 fuse ultramarine in it. Prof. Liebig stated, that platina was soon fused 

 if exposed to a charcoal fire, from the action of the silicon contained in 

 the charcoal. 



'The Measure of Nervous Force developed by a Current of Electricity, 

 by Prof. Matteucci. — This communication, which was delivered in 

 French, detailed some experiments which had been conducted with a 

 view of detecting the amount of nervous excitability. This was effected 

 by calculating the number of contractions produced in the limbs of 

 a frog in a given time by the power of a galvanic battery, the force 

 of which was known. A frog was prepared in the usual manner for gal- 

 vanic experiments, and being suspended by a pair of nippers, a weight 

 was attached to its limbs, and the animal connected with a galvanic 

 battery, a voltameter being interposed in one part of the circle. This 

 voltameter gave a correct measure of the power of the battery, and, 

 under the influence of the same current, the weight being raised over 

 a graduated scale by the contractions of the muscles, gave a measure 

 of the nervous force developed in the animal. Some other contrivances 

 were also named, by which the same end could be obtained, but none of 

 them appeared so simple as the one above described. 



Prof. Grove suggested the substitution of a galvanometer, which is 

 easily affected by weak electrical currents, for the voltameter, which re- 

 quires the force of a powerful battery. 



' On Specific Heat,' by J. P. Joule. — After examining the law of Dulong 

 and Petit, that the specific heat of simple bodies is inversely propor- 

 tional to their atomic weights, the author proceeded to detail the attempts 

 made by Haycraft, De la Rive, and Mercet, to discover the specific heats 

 of gases and liquids. The observations of Newmann and Regnault on 

 the specific heats of simple and compound bodies were next examined. 

 Mr. Joule then exhibited to the Section a table, in which the theoretical 

 specific heats of a variety of bodies impartially selected were calculated 

 on the hypothesis, that the capacity for heat of a simple atom remains 

 the same in whatever chemical combination it enters. On the whole, 

 the coincidence between the theoretical and experimental results was 

 such as would induce a belief that the law of Dulong and Petit, with 

 regard to simple atoms, is capable of a greater degree of generalization 

 than chemists have hitherto been inclined to admit. 



1 On the alternate Spheres of Attraction and Repulsion noticed by 

 Newton and others, and on Chemical Affinity,' by the Rev. T. Exley. — 





