About this time he wrote the article on “Acclimatisation” for the “Encyclopaedia Britannica”; and another on “Distribution-Zoology” for the same work.  As President of the Biological Section of the British Association he prepared an address for the meeting at Glasgow; wrote a number of articles and reviews, as well as his remarkable book on “Miracles and Modern Spiritualism.”  In 1878 he published “Tropical Nature,” in which he gave a general sketch of the climate, vegetation, and animal life of the equatorial zone of the tropics from his own observations in both hemispheres.  The chief novelty was, according to his own opinion, in the chapter on “climate,” in which he endeavoured to show the exact causes which produce the difference between the uniform climate of the equatorial zone, and that of June and July in England.  Although at that time we receive actually more of the light and heat of the sun than does Java or Trinidad in December, yet these places have then a mean temperature very much higher than ours.  It contained also a chapter on humming-birds, as illustrating the luxuriance of tropical nature; and others on the colours of animals and of plants, and on various biological problems.[5]

“Island Life"[6] (published 1880) was begun in 1877, and occupied the greater part of the next three years.  This had been suggested by certain necessary limitations in the writing of “The Geographical Distribution of Animals.”  It is a fascinating account of the relations of islands to continents, of their unwritten records of the distribution of plant and animal life in the morning time of the earth, of the causes and results of the glacial period, and of the manner of reckoning the age of the world from geological data.  It also included several new features of natural science, and still retains an important place in scientific literature.  No better summary can be given than that by the author himself: 

In my “Geographical Distribution of Animals” I had, in the first place, dealt with the larger groups, coming down to families and genera, but taking no account of the various problems raised by the distribution of particular species.  In the next place, I had taken little account of the various islands of the globe, excepting as forming sub-regions or parts of sub-regions.  But I had long seen the great interest and importance of these, and especially of Darwin’s great discovery of the two classes into which they are naturally divided—­oceanic and continental islands.  I had already given lectures on this subject, and had become aware of the great interest attaching to them, and the great light they threw upon the means of dispersal of animals and plants, as well as upon the past changes, both physical and means of dispersal and colonisation of animals is so connected with, and often dependent on, that of plants, that a consideration of the latter is essential to any broad views as to the distribution of life upon the earth, while they throw unexpected light upon those exceptional means of dispersal which, because they are exceptional, are often of paramount importance in leading to the production of new species and in thus determining the nature of insular floras and faunas.