€)/ the Island of St Christopher. 259 



the scoria? ; it is also found in a state of sublimation. Crystals 

 of alum are also abundant. The quantity of iron and sulphur 

 about the springs, I think, renders it easy to account for them, 

 from the well known action of iron upon sulphur in moist 

 places. The heat occasioned thereby would be sufficient to 

 cause the violent boiling of the water; and also to sublime part 

 of the sulphur, and to convert another part of it (assisted by 

 part of the oxygen of the water) into sulphuric acid, which 

 latter, acting upon the clay and (with the assistance of water) 

 upon the iron, forms the alum and the sulphate of iron. Wa- 

 ter is composed of oxygen and hydrogen ; when it is deprived of 

 any part of its oxygen, a correspondent portion of hydrogen is 

 set loose. I have said above, that the heated sulphur absorbs 

 part of the oxygen of the water, and forms sulphuric acid ; 

 another portion is absorbed in the formation of the sulphate of 

 iron. A considerable quantity of hydrogen is consequently set 

 at liberty, which, dissolving part of the sulphur, forms the sul- 

 phuretted hydrogen gas already described. I found some 

 pieces of clay, red on the outside, and bluish-green within. 

 These were, doubtless, at first, pieces of perfectly white clay, 

 which being saturated by a solution of green sulphate of iron, 

 of course assumed the colour ; but in a very short lime, green 

 sulphate of iron absorbs oxygen from the atmosphere, and be- 

 comes converted into the red oxide : the red colour to a small 

 distance from the exterior of the clay had been occasioned by 

 this action of the atmosphere ; but the interior, being defended 

 from it, retained its green impregnation. 



It is well known to those who are at all acquainted with the 

 rules of perspective, that when a person stands immediately 

 contiguous to the base of a perpendicular height, it appears to 

 bend over him, and the greater the height, the more the de- 

 ception is increased ; this is eminently the case in this crater: 

 for, when you stand close under Mount Misery, it appears to 

 be rent from its natural position, and to hang directly over 

 your head, as if it were instantly about to fall. For the same 

 reason, all the sides of the crater, when you are at the bottom 

 of it, appear more overhanging or perpendicular than they 

 really are ; and as there is, almost continually, a heavy, dense 

 body of clouds, resting on the summit of the mountain, the 



