V 



I 



Domestic Intelligence. 201 



whether anthracitej or charcoal were used ; but when the 

 plates were exposed to diluted acids, there was no ignition 

 so long as the circuit was completed by the former, while by 

 the latter, it must be almost unnecessary to add, the most 

 intense ignition was easily producible. This I ascrlBe to the 

 high radiant power of charcoal, which I do not believe to 

 arise from any peculiarity in its particlesj but from its extreme 

 porosity. When porous bodies are subjected to radiant matter, 

 the latter has access at once to all the particles composi] ^ 

 them, but w^hen dense bodies are exposed in the same way, 

 the exterior strata repel the radiant matter, or at most allow 

 it to combine only with their surfaces. The same structure 

 which facilitates the entrance, must of course favour the es- 

 cape of radiant matter. In consequence of the high con- 

 ducting power of metals, both as respects heat, and electri- 

 city, it were unnecessary that they should radiate in order, 

 for the igneous fluid of galvanism to pass through them; but 

 carbon being a very bad conductor of heat, is impermeable 

 to that fluid, unless in cases where it contains little caloric, 

 orwhere containing much of this fluid, circumstances will 

 allow of its separating in rays- Hence, porosity in carbon 

 is requisite to its ignition by the deflagrator. There can be 

 no doubt, that a certain regularity of arrangement^ operates 

 like porosity, in favouring the passage of radiant principles. 

 Hence, crystalline masses are often transparent, and glass 

 rapidly receives, or gives out caloric and light." 



S Spontaneous Comhustioyi. 



(Communicated by Dr. Samuel Rockwell, of Sharon, Conn.) 



" Late in the evening of the 2d of May inst. some of the 

 family of Mr. Charles Elliot, of Sharon, Conn, observed 

 Sparks of fire to be blown over the fence of his back yard, 

 from behind his barn, which was attached to a long row of 

 buildings, viz, a hatter's shop, dwelling house, &c. ^ The 

 wind, at that time, being very high, and in a direction lo 

 carry ihe fire directly on ia his buildings ; Mr- Elliot and 

 his family were immediately alarmed, and upon esamina- 

 tion, found the fire in a heap of horse-dung, which had been 

 flung out of the stable window. The fire on the top of the 

 heap was about two feet in circumference, and there was a 

 bed of coals and embers, for four inches in depth. The 



Vol. V._No. I. 26 ' 



