274 
THE GEOLOGIST. 
drifts flerived from cfranitic an.l liornblendic rocks, as well as to tliose 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 Otasjo into the adjacent provinces of Southland and 
Canterbury ; from Nelson, where they are already known to exist to an 
extent second only to tliat 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 
surrey of the province of Auckland, estimating its duration at about five 
years, with an expenditure on staff, travellinef. and publications of about 
£10,000. He recommends this equalh^ for all the New Zealand provinces 
of \A liich 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 peri\A inkles and 
other sea-shells ; these were about the level of low- water mark. He con- 
tinued boring till he came to hard beach, and still under that till he came 
to the natural hard clay AAhich lies under the city and country, and 
Thames also, far and wide. By these shells it was evident the sea had 
been \Ahere 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. 
