318 



within a stone thus formed of a silickms crust, it is the stone 

 named by the ancients JEtties, from its being supposed to be fre- 

 quently found in the nests of eagles; the contained stone being 

 termed the callimus. If the crust is empty, or contains loose sand, 

 or other earthy substances, pr is filled by any other kind of earth, it 

 is termed simply a geode : but it it contains water, it is then dis- 

 tinguished by the name enhydros. 



It cannot have escaped your observation, that the absence of 

 water from the interior of these silicious nodules is a circumstance, 

 on which Mr. Playfair chiefly founds his hypothesis ; but the fact 

 really is, that water is very frequently found in these nodules; and 

 that the stone, thus termed enhydros, is very frequently mentioned 

 by lithologists. The German mineralogists speak of them in such 

 a manner, as by no means to imply their being of rare occurrence. 

 In Germany, indeed, from the abundance in which silicious and 

 agatine nodules there exist, they might be expected to be met with : 

 but even in our own country they are also frequently seen. They 

 are found, I am informed, in and about the neighbourhood of St. 

 Vincent's rock, near Bristol ; and in no crystalline geode, which I 

 have seen from St. Vincent's rock, is there a single circumstance to 

 lead to a doubt as to their having contained an aqueous fluid. Dr. 

 Plott, in his History of Staffordshire, relates, that among the best 

 sort of iron stones, called mush, are frequently found round, or oval, 

 blackish and reddish stones, sometimes as big as the crown of one's 

 hat, hollow, and like a honeycomb within, and holding a pint of 

 sweet liquor ; which, according to the colour of the comb within 

 (whatever the stone be without) is either red or white ; and whether 

 the one, or the other, of a sweet sharp taste, very cold and cutting, 

 yet greedily drank by the workmen. It is especially found in that 

 sort of mine, the country people call the white mine, which yields 

 the best iron-stone, where the workmen commonly, upon breaking 

 a stone, find it enclosed in the centre, sometimes to the quantity 



