Park. — On Granitic Bocks in the King-country. 359 



rocks, bear so striking a resemblance to the crystalline rocks 

 of the Pikikiruna Eange and many parts of Collingwood, there 

 can be little hesitation in placing them as Silurian. 



Hitherto no granites or ancient crystalline rocks of any 

 kind have been known to exist in the North Island, and this 

 may be regarded as one of the most important geological dis- 

 coveries of the last thirty years. The discovery is not only 

 unique and interesting from a geological and scientific view, 

 but it also possesses an important bearing of an economic 

 kind. Granite and gneiss are well known as the bearers of 

 metalliferous deposits, more especially of those of tin, silver, 

 and copper, and it is possible that the exploration of the 

 broken country lying west of the Hauturu and south of 

 Kawhia Harbour may disclose the presence of valuable ores of 

 these metals. 



The central volcanic region of this Island is occupied by a 

 vast development of rhyolites and trachytes, the most highly 

 acidic of recent volcanic rocks. Their ancient prototypes, 

 granite and syenite, are the most acidic of all ancient crystal- 

 line eruptive rocks, and it would be interesting to discover if 

 the occurrence of these recent and ancient acidic rocks in the 

 same area was a mere coincidence or the result of the opera- 

 tion of natural agencies. 



At the present time there is a great diversity of opinion 

 among geologists as to the probable source or origin of the 

 solid products erupted from volcanic rents and fissures. Ac- 

 cording to one hypothesis the interior of the earth is occupied 

 by a fiery liquid mass of molten matter surging against the 

 outer shell or crust. Some believe that this molten magma 

 consists of two distinct portions — an upper layer, composed of 

 the lighter and more acidic materials, and a central portion, 

 composed of the more dense and basic materials. This hypo- 

 thesis was invented to satisfy and explain the supposed dis- 

 covery of a regular succession in the character of volcanic 

 products, according to which the acidic lavas came first and 

 the basic lavas last. 



However this hypothesis may suit the countries where it 

 originated, it certainly will not be possible to reconcile it with 

 the facts relating to the order of the eruption of igneous rocks 

 in New Zealand, as I will presently show in the following 

 statement of the character of the contemporaneous eruptive 

 rocks from the beginning of the geological record up to the 

 present time. 



It will be impossible to push our inquiries beyond Silurian 

 times for facts based on actual observations. Nothing what- 

 ever is known as to the composition of the first original crust 

 which formed on this incandescent sphere, before geological 

 time began, but its basic character may be inferred from the 



