OF NEW ZEALAND. 



361 



greens which grow from them. In many examples where the lava 

 current leaves the crater and passes into the open air, cavities of this 

 description may be observed, and indeed the adventurous explorer 

 may pass for miles underground along these caves as they are called. 

 Most of such caves appear to have been the retreat of vanquished 

 tribes, as human bones are often found in them in very great quanti- 

 ties. 



At other points of the lava current, may be found as it were 

 miniature volcanoes— points at which the lava current has been de- 

 tained while still fluid, and where the confined gases have exploded 

 with great violence, blowing up the lava as out of a crater, and spread- 

 ing the matter in pieces over the surrounding surface. I conceive 

 that the gases may have been produced, in part at least, by the 

 decomposition of water which the lava met with in its course under 

 the surface of the earth. 



Around the mountain are to be found innumerable loose stones, 

 some of enormous size, which have been ejected from the crater. 

 These have often passed to a great distance, and are in some direc- 

 tions thickly covered with sand. A person unacquainted with this 

 fact, would almost despair of being able to employ the land for agri- 

 cultural purposes, but the stones are only on the surface, showing 

 that the present soil existed before they were ejected. They are 

 used for making permanent fences. Some of them consist of solid 

 lava, others of vesicular scoria?, most of them are round and appear 

 to have assumed this shape from having been projected to a great 

 height into the air Avhiie still in a fluid or semi-fluid condition. 



The rough angular surface of the lava, which is fractured into deep 

 chasms presenting abrupt angles, and looking to the eye as a chaotic 

 mass, heaped up in wild confusion, instead of the even surface it pre- 

 sented while still liquid, is evidently owing to the changes of 

 temperature which it has undergone, and the contraction of the par- 

 ticles consequent thereon. The enormous cracks and disjointed frac- 

 tures are evidence of the intense heat which once pervaded the molten 

 mass, and now make it difficult to believe that it ever presented an 

 even surface. 



I send you some of the earths which abound in the neighbourhood, 

 convinced that they have all issued from the volcano in the form of 

 mud or ashes, and as the constituents, and the peculiar condition of 

 such may involve questions interesting to the geologist, I thought 

 you would probably be pleased to receive them, and might cause them 

 to be analysed. I am fully convinced that not one of the layers of 



