The elevated spot which cracked in so remarkable a manner, being nearly surrounded by a _belt_ of low wet ground, the congelation of the water in this ground by the intense cold, would of course produce a very great expansive effort towards the elevated ground. This, not only on account of its elevation, but from its containing less water, would not be able to exert an equal counteracting effort. The surface of the ground, therefore, (without at all disturbing the unfrozen earth below,) was, by the expansive effort of the freezing water, _pushed along_ towards the elevated spot. This spot being possessed of a certain power of resistance derived from its gravity, and from the freezing of the water in it, would not immediately give way; but the whole surface, it is probable, gradually rose for some time, while the expansion was going on and increasing. A cavity would thus be produced between that superficial layer of frozen ground which was rising, and the unfrozen ground below. This cavity would of course be filled with air derived from the atmosphere, and from the porousness of the ground below. When the place came to be overflowed, water would immediately rush in through any fissure, and this hydraulic and hydrostatic effort would force the air out at any orifice, and thus blow the water up with it. This was probably the cause of the agitation of the water, and of the bubbling of air, and of the throwing up of the water at intervals, observed by the boys on the 3d of March. The effect of the water covering the ground, would be to weaken its cohesion derived from frost, and as there were probably hundreds of tons of pressure, the vaulted ground, when sufficiently weakened, gave way with a loud explosion and a violent concussion, as heard by Mr. Sheldon's family, a few hours after the facts observed by the boys. The parts of the arch now fallen in, (so to speak) necessarily either overlapped, or rose in ridges, piece being pressed against piece, as described and figured by Mr. Hitchcock. We are indebted to this gentleman for his delineation of this singular case. The freezing of water, and its attendant expansion, are productive of multiplied and very diversified phenomena upon our globe, whether we contemplate them in the delicate spiculæ of hoarfrost, the six-rayed stars of snow, or in the stupendous glaciers of the Alps, and the awful icebergs of Greenland. _Cambridge, January 25, 1819._ PROFESSOR SILLIMAN. _Dear Sir_, If the following observations are worthy of a place in your valuable Journal, please to insert them, and oblige yours, with real esteem, J. F. DANA. ART. XIV. _On a New Form of the Electrical Battery, by_ J. F. DANA, M. D. _Chemical Assistant in Harvard University, and Lecturer on Chemistry and Pharmacy in Dartmouth College_.