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green incrustation, deposited upon a fragment of the shelly 
Oolite of the neighbourhood, and it is here recorded with much 
pleasure as a native product, to be inserted in the list of the 
mineral species of Gloucestershire. 
The species given in the list referred to are, for the most 
part, of a sober cast, including few if any of the fairer forms 
of inanimate nature, and certainly “no agate stone, fit for the 
fore-finger of an alderman.” Still, apart from any value in 
itself, we may fondly hope that the unexpected discovery of 
Vivianite will quicken the student to gain power of vision and 
acuteness in detecting similar objects. 
A few remarks may be here offered concerning the compo- 
nents of the hydrated phosphate of iron. The sources of the 
elements of this combination of oxide of iron and phosphoric 
acid are clearly evident. The phosphoric acid must have been 
derived from the shelly detritus and the ochraceous matter of 
the Oolitic rocks; for ochre or limonite is a variety of hydrated 
oxide of iron, containing from 30 to 60 per cent. of iron oxide, 
and is apt to be combined with phosphoric acid, supposed to be 
derived from the decayed vegetation in swamps, acting on the 
oxidated iron of the adjacent rocks. Umber, said to be found 
abundantly in the Forest of Dean, is also an earthy variety of 
it, containing manganese. The union between the phosphoric 
acid and the iron is effected in nature’s laboratory. Phosphoric 
acid, on account of the number of its modifications and the 
facility with which it lends itself to form organic compounds 
in the animal system, has been designated by an eminent 
chemist the organic acid—a veritable harlequin in disguise. 
Whilst iron, the other element in Vivianite, has been termed, 
par excellence, the organismal metal, having its special value in 
the animal economy;—bones, shells, tissues, and even the blood 
itself, contain ferric oxide. Its presence has not been unnoticed 
by the poets. Tennyson, in “The Princess,” makes the father 
of his heroine exclaim, when his stately daughter shows no sign 
of relenting toward the wounded Prince— 
‘“‘T’ve heard that there is iron in the blood ; 
And I believe it.” 
