80 



THE GEOLOGIST. 



rocks far below the surface, which have never appeared ; and that the 

 gradual disappearance of the anthracitic tendency has been simply the 

 diminishing distance from the heat which has caused the change. The 

 question may be asked, Why are only the " North Crop coals " anthra- 

 citic, while the " Upper Measure coals," which are worked only a few 

 miles distant, are bitumJnous ? For instance, at Trimsacau, near 

 Kidwelly, the coals are stone-coals, while at Llanelly, only six miles 

 distant, the coals (upper measure) are bituminous. I consider the 

 reason to be that the changes were subsequent to the deposition of 

 the lower measures and prior to the upper ones ; for we must not 

 forget the vast geologic times that passed between the formation of 

 the upper and the lower measures, during the deposition of the 

 immense thickness of Pennant rock. According to this notion, the 

 anthracitic change was all completed before the deposition of the 

 upper measures. If the change were going on now, I cannot under- 

 stand how the upper measures, which are so near the seat of change, 

 can escape the same effects. In addition to what I have stated, I may 

 add that in all the accounts of anthracitic coal-fields which I have 

 looked through, whether belonging to the old coal-period or to the 

 secondary eras, I have observed that disturbances and the presence 

 of igneous rocks are described as existing in the great majority. 



FOREIGN CORRESPONDENCE. 

 By Dr. T. L. Phipson of Paris. 



]': 



Shifting Sand-hills of the Mediterranean — Sand-hills or Dunes on the a 

 Coast of Flanders — Encroachment of the Sea — Vegetation of the Dunes 

 — Subterraneous Noises — Crystalline forms of Anglesite — Analysis of a p 

 Meteorite — Minerals in Aerolites — Meteoric Stones and their relations d 

 to Geology — The Volcano in the Island of Bourbon —Temperature of a 

 the Earth's crust at inconsiderable depths — Activity of Mount Vesuvius c 

 — Earthquakes in Turkey — Submarine Volcano near Leghorn — 6 

 Erratum : Iron-alum. , >^ 



1' 



The learned Geologist of Montpelier, M. Marcel de Serres, has just 

 communicated to the Paris Academy of Sciences the following facts 

 concerning the dunes, or shifting sand-hills, of the French Medi- \ 

 terranean coasts. These sands are first thrown upon the shore by 

 the sea ; when dry, they are carried inward by the winds, to the 



