274 



THE GEOLOGIST. 



drifts derived from granitic and hornblendic rocks, as well as to those re- 

 sulting from the detrition of Silurian and other slates. 7. That it is pro- 

 bable the auriferous system of rocks, the supposed Silurian slates, extends 

 from the province of Otago into the adjacent provinces of Southland and 

 Canterbury ; from Nelson, where they are already known to exist to an 

 extent second only to that in Otago, and where, indeed, " gold-fields " have 

 been successfully worked for a considerably longer period, in Canterbury; 

 and from Auckland into Wellington and adjacent districts, though to what 

 extent remains to be determined by actual survey and experiment. 8. Con- 

 trasting the Northern with the Middle Island of New Zealand, it is pro- 

 bable that the latter is more extensively and largely auriferous than the 

 former ; that in the former the auriferous quartzites are developed out of 

 proportion to the derived drifts, while in the latter the reverse is the case ; 

 and that, should this supposition prove to be correct, the character of the 

 gold-mining in the two islands will necessary differ most materially. 

 9. Speaking in general terms, auriferous rocks may be said to extend 

 throughout the New Zealand islands, the exceptions being where they are 

 interrupted by recent volcanic formations, traps of various ages, mostly 

 Tertiary, limestones of various ages, extensive Tertiary beds, and other 

 geological series or systems. 



Dr. Lindsay strongly advocates an immediate systematic geological 

 survey of tbe province of Auckland, estimating its duration at about five 

 years, with an expenditure on staff, travelling, and publications of about 

 £10,000. He recommends this equally for all the New Zealand provinces 

 of which geological surveys have not yet been made ; pointing to the 

 example of Otago, which has recently appointed a Government geologist, 

 who is now engaged on a three years' survey of that most interesting 

 province. 



Wren's Section at St. Paul's. — The account of the geological section 

 presented in the excavation of the foundations of St. Paul's may be worth 

 a record here. It is from ' The Parentalia,' published by Sir Christopher 

 Wren's son, in 1750 : — 



" It has been before observed that the graves of several ages and 

 fashions, in strata or layers of earth one above another, particularly at the 

 north side of St. Paul's, manifestly showed a great antiquity from the 

 British and Roman times, by the means whereof the ground had been 

 raised ; but, upon searching for the natural ground below these graves, 

 the surveyor observed that the foundation of the old church stood upon a 

 layer of very close and hard pot-earth, and concluded that the same ground 

 which had borne so weighty a building might reasonably be trusted again. 

 However, he had the curiosity to search further, and accordingly dug wells 

 in several places, and discovered the hard pot-earth to be, on the north 

 side of the churchyard, about six feet thick and more, but thinner and 

 thinner towards the south, till it was, upon the declining of the hill, scarce 

 four feet ; still he searched lower, and found nothing but dry sand, mixed 

 sometimes unequally, but loose, so that it would run through the fingers. 

 He went on till he came to water and' sand, mixed with periwinkles and 

 other sea-shells ; these were about the level of low-water mark. He con- 

 tinned boring till he came to hard beach, and still under that till he came 

 to the natural hard clay which lies under the city and country, and 

 Thames also, far and wide. By these shells it was evident the sea had 

 been \Uiere now the hill is on which Paul's stands. The surveyor was of 

 opinion the whole country between Camberwell hill and the hills of Essex 

 might have been a great frith or sinus of the sea, and much wider near the 

 mouth of the Thames, which made a large plain of sand at low-water, 



