252 GEOLOGY OF THE ISLE OF WIGHT. 



For a short time the coal-seam In the Bagshot Beds in Alum Bay 

 was worked, but it is of very little value. Alum was formerly 

 manufactured in the Island from the clays of Alum Bay, and as 

 early as 1579 at works in Parkhurst Forest. The Crown used 

 formerly to monopolise the whole of the alum, and proper people 

 were appointed to gather and preserve it for Government. This 

 practice commenced with Queen Elizabeth, who sent a mandate to 

 Richard Worsley, then Captain of the Isle of Wight, in order to 

 ascertain the truth of what she had heard, and a warrant was 

 issued, dated 7th day of March 1561, to search for " certan Oure 

 of Alume." 



Iron pyrites was collected on the shore about Shanklin, and 

 carried by boat to London, during the last century.* The clay 

 ironstone, which is found in considerable quantities lying loose 

 upon the shore at the foot of the cliffs between Yarmouth and 

 Hamstead ledge, Avas collected on the beach and sent to Swansea, 

 to be smelted into iron. 



Phosphatic Nodules. 



Reference has frequently been made in the preceding pages to 

 the occurrence of phosphatic nodules at various horizons, but 

 more especially in the Cretaceous Rocks. In consideration of the 

 great economic importance of such nodules, it is proposed to 

 devote a few lines to describing their mode of occurrence and 

 composition. 



The Wealden Beds. 



Phosphate of lime occurs in these beds, but in small quantities 

 only, in the numerous fragments of lignite, which are found at 

 almost all horizons in the vai'iegated marls. The wood is similar 

 in appearance to that which occurs in the Lower Greensand, and 

 which is stated by Messrs. Paine and Wayt to be rich in phos- 

 phoric acid. They remark that the fossil forest at Brook Point is 

 probably impregnated with phosphoric acid. It should be noted, 

 however, that most of these lignites are encrusted with, or traversed 

 by threads of iron pyrites. They are moreover too thinly scattered 

 throuffh the clay to be profitably mined. 



The Lower Greensand. 



A specimen of the fossil wood which occurs sporadically in so 

 many of the beds of the Lower Greensand was analysed by 

 Dr. T. L. Phipson with the following result : — \ 



* Warner. History of the Isle of Wight, pp. 261 and 263. 1795. 

 \ On the Phosphoric Strata of the Chalk Formation. Journ. Eoy. Ag. See. 

 England, vol. ix, p. 82. (1848.) 



X Chemical News, vol. vi. p. 194. (1862.) 



