346 Transactions. — Geology. 



known as the trap series, largely distributed over the earth's surface, and 

 as they contribute in a larger degree than any other class of rocks to the 

 economy of vegetable and animal life, I may be excused in alluding here 

 to their properties in this respect. In their composition they contain in 

 considerable quantity potash and other salts necessary to the growth of 

 plant life, and when decomposed by the sun's heat and rain, which destroy 

 their cohesion, the pulverized particles are washed down into the valleys 

 and form our best soils for growing grass and cereals. It is possibly one 

 of the best tests in looking after new country for settlement, to examine the 

 character of the rocks surrounding the country you are traversing, and you 

 may rest assured that if this trap series is the prevailing rock the valleys will 

 be rich and fertile. We have a very good example of this in that part of 

 our township called The Wood, where we have that rich sedimentary deposit, 

 where we grow hops and vegetables. That district has at some former period 

 been a lagoon of comparatively still water, the force of the Maitai current 

 being broken by the bluff at Mr. Huddleston's property, and the sediment 

 from the degraded trap dykes I have before mentioned, finding its way in 

 solution into this lagoon, gradually deposited itself into a rich alluvium, 

 which proves so fertile for cereal crops. I conclude, therefore, that this 

 alluvium is chiefly a decayed trap deposit, because no other rock in the 

 Maitai series from its composition could give out soil of this description. 

 The dyke from which this deposit has chiefly come runs from Mr. Huddle- 

 ston's Bluff, past the back of Mr. Sharp's house, and again shows itself on 

 Mr. Curtis's property, on the Wakapuaka Eoad, the worn-down face of 

 this ridge being the deposit I have now mentioned. 



Probably our greatest misfortune in the Province of Nelson is, that we 

 have so little of this class of rock, but are surrounded on all sides right on 

 to the west coast by slates, schists, and rocks of a quartzose character, and on 

 the east by the Dun Mountain Eange, by slates and a variety of rocks of a 

 magnesian class, extending from D'Urville Island in the north, to the Top- 

 house at the head of the Wairau Valley — -all these rocks I have mentioned 

 being from their composition unfavourable to plant life, and the alluvium 

 from them being considered country of a third or fourth class. We are 

 not, however, left without some comfort in having at different points in our 

 surroundings rocks of a more fertile class, such as a volcanic trap, granites, 

 and limestones of various kinds, and some others containing felspar in con- 

 siderable quantity, which has given the district some rich alluvial soil. We 

 are very apt, in travelling through a country, to pass along giving very little 

 heed to the character of the rocks surrounding us on every side, but there 

 is little doubt that the fertility or non-fertility of a country depends very 

 much on the character of the rocks by which it is intersected. 



