GEOLOGICAL FEATURES OF OUR GLOBE. 
489 
The probable effect of cutting through the Isthmus of 
Panama mighty in a similar way, overwhelm some of the 
West India Isles, and diverting the gulf stream from the 
shores of Great Britain, thereby totally changing its climate, 
and taking away its present remarkable exemption from 
extreme cold. 
New Zealand, like Britain, is also indebted to one if not 
two warm currents from the tropics, sweeping down either 
coast, and attesting their presence by the various seeds from 
tropical islands which are continually being drifted on its 
shores. 
The effects of volcanic agency may be also alluded to, 
their destructive results are seen, without sufficiently consi- 
dering the benefits they confer : by their upheaving power 
they enable man to examine the very bowels of the earth, 
and appropriate their riches to his use ; they also are to be 
viewed as the safety valves of the earth, which, whilst in 
action, relieve the surrounding regions from the apprehen- 
sion of earthquakes, whilst the earth is enriched by the various 
substances ejected. In proportion to the quantity thrown out, 
will be subsidences and the formation of lakes ; at the foot of 
Tongariro, New Zealand^ chief volcano, is the largest lake 
of that island, nearly thirty miles long and as many broad. 
MOUNT METAL AND PEMBROKE PEAK, MILFORD SOUND 
