351 



ance, we perceive, is quite lost ; and, in the intervening part, the 

 gradual departure from a striped, to quite a plain appearance, may 

 be observed : whilst frequently the existence of the soft bituminous 

 state will appear, from the wavy and contorted directions of fibrous 

 stripes, which are indubitably of a ligneous origin. Nor does any 

 difference of physical properties exist between this and the ligni- 

 form pitch-stone already described. With respect to their chemical 

 properties, there exists a very close agreement, as will appear from 

 the following experiments. 



Mr. Pepys exposed 50 grains of pitch-stone, and 100 of pure 

 nitrate of pot-ash, to the same treatment as he had subjected the 

 same quantities of opaline fossil wood and nitrate of pot-ash, and 

 reported that the phenomena which resulted were precisely the 

 same. 



At Menil le Montant, also at Saint Ouen, near Paris, and in 

 several other parts of France, have been found a stone which is 

 of a greyish colour, sometimes mottled with blue on its surface, 

 opaque, generally of a tubercular form, and showing at its fracture 

 a slight lustre of the greasy kind. It was first described by Delabre 

 and Quinquet, who very properly considered it as- a new kind of 

 pitch-stone; its hardness, specific gravity, and fracture, as well as 

 its kind of lustre, warranting them in this opinion *. It was named, 

 from the place where it was first found, Menilite, and was consi- 

 dered as a variety of the pitch-stone, being therefore termed, by 

 some, blue pitch-stone ; but it has been supposed by others to be- 

 long rather to the magnesian genus of stones, such as the pot-stone, 

 steatites, and serpentine. 



The experiments of the justly celebrated Klaproth, which induce 

 him to consider this fossil, as a variety of the semi-opal, approach- 

 ing to flint (feuerstein) serve strongly to corroborate the opinion I 



* Journal de Physique, Sept. 1787, p. 21$. 



