380 Queries and Answers. 



hardness of the stones according to age, though evidently all 

 the same variety of sandrock, are clearly discernible in the 

 various repairs which have, from time to time, been made ; 

 the newer pieces of stone cracking and crumbling when struck 

 with a hammer, the older remarkably firm. The mortar, also, 

 in the most ancient part of the building, as I have observed, 

 indeed, in many of the old castles in Wales, is as compact and 

 hard as any stone I ever met with. Sir Humphrey Davy, in 

 his last and interesting little work, Consolations in Travel ; or, 

 the last Days of a Philosopher, observes (p. 119.), that some of 

 the largest and most magnificent ruins in Rome, such as the 

 triumphal arches and the Colosseum, owe their duration to 

 the travertino of which they are built ; originally M formed by 

 a variable source of the most perishable materials," having 

 hardened by time. This travertino is procured from the 

 Velino, near Terni, a cascade containing calcareous matter 

 brought down by the Apennines, dissolved by carbonic acid 

 gas, which " deposits marble, which crystallises, even in the 

 midst of its thundering descent and foam, in the bed in which 

 it falls." {Id., p. 113.) 



A paper, by one of your travelling correspondents, stating 

 the materials which some of the most remarkable monuments of 

 ancient and modern times are built with ; and particulars as to 

 how they have stood the weathering, as it is generally termed ; 

 mentioning, at the same time, the mean temperature of the 

 climate, quantity of rain falling per annum, prevalent winds, 

 and the like ; would be highly interesting to your geological 

 readers. — W. Perceval Hunter. Sandgate, July 10. 1835. 



The Isle of Sheppey ^ Facts and Questions, on the Geological 

 Conditions of. — In a ride round the Isle of Sheppey, last week, 

 I collected and purchased a great variety of fossil fruits and 

 berries, part of a fossil lobster, some crabs, a large nautilus ; 

 and very nearly succeeded in procuring a tortoise, which, un- 

 fortunately, had been sold only a few hours before my arrival, 

 of a woman collecting iron pyrites on the beach. My gratifi- 

 cation at possessing what appeared to me a most interesting 

 and durable collection of fossils was, however, materially 

 diminished on paying a visit, on my return to Sandgate, to 

 Mr. Hills's beautiful collection, at Lympne, in greensand and 

 gault fossils, as extensive as any in the kingdom. Several 

 specimens in his cases have fallen to pieces ; and he assured 

 me it was more or less the case with every thing from Sheppey, 

 owing to the immense quantities of iron pyrites contained in 

 the fossils. He recommended me to wash mine well over 

 with turpentine and lamp oil : but even this, he said, was not 

 sufficient. [See in VI. 480.] 



Can any of your Correspondents recommend something more 



