14 Dr. Maycock on the Geology of Barbadoes. 



mineral oil, and asphaltum ; and probably many other minerals, 

 which I have not myself met with. In addition to the above, 

 however, I have found in a hill of Scotland, which, from the 

 white appearance of its broken clayey cliffs, has been improperly 

 termed Chalky Mount, a bed of porphyritic slate, or clinkstone 

 porphyry. It is about eighteen inches in thickness, lies between 

 beds of very loosely cohering sandstone, and dips to N. E. at an 

 angle of 30°. The occurrence of clinkstone porphyry in this 

 situation is deserving attention ; for, as the great mass of the 

 hilly district is composed of minerals which I suppose to be 

 most properly associated with the independent coal formation, 

 this fact will stand as an additional proof of the existence of a 

 trap formation of anterior date, as first noticed by Professor 

 Jameson, to that which has been denominated by Werner, the 

 newest flotz trap formation, to which the clinkstone porphyry 

 has been supposed to belong. This part of the island evinces 

 very perfect stratification, the strata being generally much in- 

 clined, and not unfrequently distorted. 



The petroleum, or mineral oil, the green tar, as it is here 

 termed, occurs in abundance in some situations, exuding from 

 crevices in the clay-hills. It is collected on the surface of 

 water in holes dug for the occasion, and is employed for various 

 economical purposes. The gypsum occurs in fragments, in 

 crystals, and distinct concretions, from a very small magnitude 

 to such as weigh several ounces, disseminated through clay- 

 beds. The fullers' earth is found in Chalky Mount, where I 

 have seen it in a bed a few inches thick, composed of alternate 

 laminae of fullers' earth and yellow earth. The clay, which is 

 abundantly distributed through the hilly district, is not very 

 pure, being generally charged with iron, petroleum, or calca- 

 reous matter ; but in most places it answers sufficiently well for 

 the manufacture of coarse ware and bricks ; and accordingly 

 there are several pot-kilns in the parishes of St. John, St. 

 Joseph, and St. Andrew. Furnaces are frequently constructed 

 in this island of unburnt bricks ; the cement used on such occa- 

 sions being a paste of the same kind of clay as that of which the 

 -bricks are made. Upon the application of heat, the whole be- 



