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TROPICAL NATURE 
IX 
of comparing the productions of one country with those of 
another ; of investigating the physical and biological relations 
of islands and continents ; of watching the struggle for 
existence in regions where civilisation has not disturbed the 
free action and reaction of the various groups of animals and 
plants on each other; and, what is perhaps more important 
still, the ample leisure to ponder again and again on every 
phase of the phenomena which presented themselves, free 
from the attractions of society and the disturbing excitement 
of daily association with contemporary men of science, — 
these are the conditions most favourable to the formation of 
habits of original thought, and the months and years which 
at first sight appear intellectually wasted in the companion- 
ship of uncivilised man, or in the solitary contemplation of 
nature, are those in which the seed was sown which was 
destined to produce in after years the mature fruit of great 
philosophical conceptions. Let us then first glance over the 
Journal of Researches , in which are recorded the main facts 
and observations which struck the young traveller, and see 
how far we can detect here the germs of those ideas and 
problems to the working out of which he devoted a long and 
laborious life. 
The Journal of Researches 
The question of the causes which have produced the dis- 
tribution and the dispersal of organisms seems to have been 
a constant subject of observation and meditation. At an 
early period of the voyage he collected infusorial dust which 
fell on the ship when at sea, and he notes the suggestive fact 
that in similar dust collected on a vessel 300 miles from land 
he found particles of stone above the thousandth of an inch 
square, and remarks : “ After this fact, one need not be sur- 
prised at the diffusion of the far lighter and smaller sporules 
of cryptogamic plants.” He records many cases of insects 
occurring far out at sea, on one occasion when the nearest 
land was 370 miles distant. He paid special attention to the 
insects and plants inhabiting the Keeling or Cocos, and other 
recently formed coralline or volcanic islands ; the contrast of 
these with the peculiar productions of the Galapagos evidently 
impressed him profoundly ; while the remarkable facts pre- 
