98 The Columnar Basalt of Pouh Hill. 



but when it is deposited from animal fluids the form of the 

 crystals is often much modified." The same authority says that 

 " pure uric acid is a white crystalline powder, requiring 10,000 

 parts of cold water for its solution." This being the case 

 would account for no harm being done to my crystals by im- 

 mersing them in drops of fresh water. The urates, although 

 sparingly soluble, are much more so than uric acid. Urate of 

 potash (neutral) is soluble, according to Miller, in forty-four 

 parts of cold water ; the urate of soda is somewhat less soluble, 

 and the urate of ammonia is soluble in 18.00 parts of cold 

 water. The Ml orographic Dictionary gives drawings of crystals 

 of urates, none of which correspond — as some of its repre- 

 sentations of uric acid do — with those in the Artemia, but 

 it adds that their forms " are not very characteristic" In 

 the article Uric Acid, in the same work, it is observed that 

 ' ' the crystals forming a natural deposit are almost invariably 

 coloured, from combining with the colouring matter of the 

 urine." Little crustaceans like brine shrimps would not s be 

 expected to colour this substance, and in all my specimens it 

 was pure white, like glass. 



I should recommend anybody looking for these crystals to 

 cut off the abdominal segments before using any compression. 

 If the entire animal is compressed, too much mess is made to 

 see them clearly, and unless the abdomens are placed in clean 

 fresh water, the observer is pretty sure to be troubled by the 

 deposit of salt from the strong brine in which the creatures 

 dwell. 



THE COLUMNAR BASALT OF POUK HILL, 

 SOUTH STAFFORDSHIRE. 



Secretary of the Dudley and Midland Geological Society. 



Wk are bo accustomed to regard the Giant's Causeway, and 

 FingaTs Cave in Staffa, as the only British examples of 

 columnar basalt, that perhaps the title of this chapter may 

 appear indicative of some aew discovery. This is not the case, 

 however, for the peculiar columnar structure of the Igneous 

 rocks which occur in connection with the coal-measures of 

 South Staffordshire, and also of the Clee Hills farther west, 

 has been long known and recorded; but the (nee of basalt, 

 which is now exposed at the extensive quarries of Pouk Hill, 

 near Walsall, affords, perhaps, a liner section of this remark- 



