VOLTAIC ACTION. 397 



the apparatus. It is stated by M. Pouillet 

 Scrope, on the authority of Dolomieu, corrobo- 

 rated by his own observations, that very little 

 heat is radiated from a mass of red hot lava 

 that at the distance of a few feet, the thermo- 

 meter is scarcely affected by it, which induced 

 Dolomieu to suppose that its fluidity was due to 

 some other cause than caloric. (Scrope on Vol- 

 canos, p. 20.) 



The reason why incandescent lava does not 

 radiate heat like coal, wood, &c. when in a state 

 of ignition, is doubtless owing chiefly to the 

 greater attraction of metallic and rocky masses 

 for caloric, than combinations of animal and 

 vegetable matter, as explained under the head of 

 radiation. 



It has been long known, that the most intense 

 electrical phenomena are displayed during vol- 

 canic eruptions. If it be inquired why persons 

 near to a mass of incandescent lava experience 

 no electric shock, it may be answered, that no 

 shock is received from a voltaic battery of large 

 plates ; nor should we be able to discover that 

 any electricity was evolved were it not con- 

 ducted off by the connecting wires to the ex- 

 tremities of the pile : even then, it exhibits 

 chiefly the phenomena of concentrated caloric, 

 and but slight indications of electricity. 



Mr. Scrope has given a highly graphic de- 

 scription of the electrical action that accom- 



