Intelligence and Miscellaneous Articles, 155 



final result, therefore, after an action of a certain duration, must 

 differ according to whether one of the elements separated is solid, 

 liquid, or gaseous at the surrounding temperature, and must depend 

 on the more or less elevated temperature produced by the passage of 

 the spark, as well as the recompositions which may be effected in 

 the vicinity of the latter. M. Thenard placed himself in conditions 

 such that the calorific action , extended only the least distance 

 possible around the electrified points. Instead of sparks bursting 

 forth in a eudiometric tube, he made use of the electrical effluvium 

 — that is to say, more or less obscure discharges produced from 

 plaee to place among the gaseous particles themselves. Eor this 

 purpose he had recourse to the simple and ingenious arrangement 

 of apparatus devised by M. Houzeau for the production of ozone, 

 as the conditions necessary to that allotropic transformation of 

 oxygen appeared similar to those which he proposed to utilize. 

 This arrangement permitted him, besides, to submit to the electric 

 influence successively and in distinct portions any volumes what- 

 ever of gas or vapour. 



Several important additions to and modifications of this mode of 

 experimentation have been made by M. Arnould Thenard, and very 

 carefully studied for the purpose of ascertaining the most favour- 

 able conditions for the production of ozone as well as for the de- 

 composition of carbonic acid. His observations led him to perceive 

 that it is preferable to produce the electric effluvium between 

 smooth surfaces of glass instead of \ between metallic conduc- 

 tors. He likewise saw that the action of electricity disaggre- 

 gates glass at its surface, covering it with a fine powder which ends 

 by transforming little by little the effluvium into sparks — that is to 

 say, gives to the discharge a form which not only does not produce 

 the effects of the effluvium, but may even destroy them. By re- 

 moving this powder the efficacious action of the smooth tubes is 

 reestablished. In certain circumstances which he indicates, elec- 

 trochemical deposits in the tubes may give rise to the same effects. 



His researches relate particularly to carbonic acid, the partial de- 

 composition of which has, from the end of the last century, been 

 the subject of several investigations on account of the action of the 

 spark upon this gas being opposite to its action upon a mixture of 

 carbonic oxide and oxygen, the two latter gases being capable of 

 reconstituting carbonic acid in a eudiometer. He has ascertained 

 that, with a very gentle current of carbonic acid circulating in the 

 special apparatus he makes use of, decomposition into carbonic 

 oxide and oxygen may reach 2Q-5 per cent, of its volume ; while, 

 as De Saussure observed, if we operate by means of sparks, it does 

 not exceed 7*5 per cent. 



He likewise shows that the preceding mixtures, containing as 

 much as 26*5 per cent, of decomposed carbonic acid, revert in the 

 gaseous state to 7*5 per cent, in the eudiometer — the greatest ele- 

 vation of temperature due to the sparks in the latter experimental 

 conditions doubtless not rendering possible, as shown by M. Eer- 

 thelot's experiments, an explosive mixture of carbonic pxide and 



