166 Intelligence and Miscellaneous Articles, 



containing a certain proportion of vegetable debris. The organic 

 matter has undergone a special mineralization, producing a bitumi- 

 nous, in place of the ordinary anthraciferous substances. This ope- 

 ration is not attributable to heat, nor of the nature of distillation ; 

 but is due to chemical reaction at the ordinary temperature and 

 under the normal conditions of the climate. After the solution 

 and removal of the bitumen from wood passing into asphalt, the 

 remaining organic structure presents peculiar appearances under the 

 microscope. 



The occurrence of asphalt in New Granada and the Valley of the 

 Magdalena in all probability indicates the presence of the Newer 

 Parian strata in those districts. 



The phenomena of salses or mud-volcanos (common in Trinidad 

 and on the mainland) are referred by the author to the chemical 

 decomposition and changes (such as the formation of asphalt) which 

 are in operation in the lignitic strata of this formation, since the 

 evolved gases are inflammable, and the discharges of muddy matter 

 are usually accompanied with asphalt and petroleum, 



•Thermal waters are not rare. Those of Trincherras, issuing from 

 mica-schist, possess a variable temperature, according to the follow- 

 ing determinations : —Humboldt in 1800, 194°; Boussingault in 

 1823, 206°; and the author in 1859, 198°. The hot springs at 

 Chaguaranal near Pilar are much more interesting, as the water is 

 discharged, from a limestone of the Older Parian series, at a tempe- 

 rature even above the boiling-point. It deposits carbonate of lime, 

 sulphur, &c. 



A souffriere near by, issuing from an Older Parian sandstone, 

 yields a variety of purely siliceous deposits, chalcedonic and agati- 

 form. The siliceous cement of the sandstone, being a hydrate, and 

 soluble in acidulated water, has probably afforded the material for 

 these deposits. The colour of these siliceous sinters are traceable, 

 some to the sulphur (yellow), others to the decomposing leaves 

 (brown, &c). 



Earthquakes are of ordinary occurrence. The earthquake of 

 1853 destroyed the town of Cumana. 



The probable relations of the Cretaceous rocks of Venezuela with 

 those of New Granada, Peru, Chili, Brazils, and the Straits of Ma- 

 gellan were alluded to by the author. 



XIX. Intelligence and Miscellaneous Articles, 



ON THE FORMATION OP ICE AT THE BOTTOM OF WATER. 

 BY M. ENGELHARDT. 



''PHE author in 1829, undertook some experiments with a view to 

 explain the formation of ground-ice and has since repeated 

 them. 



He took three iron boilers about 660 millims. in diameter, and a 

 wooden trough about the same dimensions. These were severally 

 filled with river- water of the temperature +2°: the temperature of 

 the air was —2° during the day, and sank to —5° during the night. 

 They were supported at a distance of 20 centims. from the ground, so 



