70 Scientific Congress at Florence : — 



undergoing any action, change if they are heated in any way what- 

 ever. 



M. Perego related his experiments on the development of electri- 

 city by the immersion of bodies in mercury. One of the substances 

 which succeed the best is the felt used in making hats. 



M. Mossotti read a memoir on the explanation of the dispersion of 

 light in the undulatory theory. 



M. Dini communicated some experiments relative to the influence 

 of heat on capillary attraction. 



M. Orioli communicated the observation of a kind of light seen by 

 an individual on his toes. M. Boyer noticed a similar observation. 

 These two physicists explain these phsenomena by supposing a 

 morbid secretion of electricity. — M. Matteucci cannot admit this 

 explanation, not seeing how^ a luminous electric charge can be pre- 

 served without discharging itself upon bodies which are in contact ; 

 he thinks that these phsenomena should rather be referred to those 

 which relate to the phosphorescence of rotten wood, fish, &c. 



M. Matteucci exhibited an apparatus for electrostatic inductions. 

 He describes an apparatus which he calls a differential inductometer, 

 and which is composed of a spiral plane placed between two similar 

 spirals ; these may approach more or less to the intermediary spiral, 

 and their extremities may be united together so as to produce two 

 currents which circulate in contrary directions. He mentioned 

 some contrary results which he found in studying these induced 

 currents by means of magnetizing, by the galvanometer, and by the 

 hole made in paper by the spark of induction. 



M. Pacinotti described two experiments which appeared to him 

 contrary to the theory of Ampere. He has a cylinder of soft iron, 

 which is hollow ; he introduces into the internal central part of this 

 cylinder a spiral, and places a similar spiral at the exterior. M. Pa- 

 cinotti has found that the current of the external spiral does not 

 give an induced current in the internal spiral, and that a current in 

 the internal spiral does not magnetize the cylinder of soft iron. 



M. Mahlmann of Berlin |_read an extract from a work on the 

 distribution of heat on the surface of the earth. 



M. Giazi read a description of the effects produced by lightning. 

 He exhibited some pretty vitrification of stones, some black and 

 yellow traces left on a wall, and a nail magnetized by means of the 

 thunder stroke. 



The Count Scopoli mentioned the causes of the inundations of 

 Lombardy, and added to the known causes the slow destruction of 

 certain artificial lakes which are found on the declivities of the 

 mountains. 



MM. Stefani and Jordani presented models of electric telegraphs, 

 and of electro-magnetic telo-typographs. 



M. Cini exhibited a singular reproduction of a drawing, which is 

 produced at the end of a certain time on the plate of glass which 

 covers this same drawing. 



M . Marianini read a summary of the experiments made by him on 

 induction. He thinks he can establish as a fact, that the current of 



