After eight years in Australia Belt returned to England, married, and was successively manager of mining companies in Nova Scotia, North Wales, and Nicaragua, sandwiching in between these appointments a visit to Brazil to report upon some gold mines in the province of Maranham. In whatever part of the world his work took him he turned for rest and relaxation to the branches of natural science for which the locality offered the greatest opportunity.

In Nova Scotia he began those investigations into the cause and phenomena of the glacial period which were to be the study of the last years of his life, and to which he himself attached the greatest importance. In Wales he took up the question of the age of the rocks in the neighbourhood of Dolgelly, and after much study of their fossils proposed the now accepted classification of the Lingula flags of the Lower Silurian system into the Maenturog flags and slates, the Festiniog flags, and the Dolgelly slates. The collecting of lepidoptera was his chief amusement in Brazil, where he made his first acquaintance with the teeming life of the torrid zone and laid the foundation for those observations on tropical nature which his longer stay in Nicaragua gave rise to, and which are recorded in this book.

After his return from Central America, his services were in great request as a consulting mining engineer, and the succeeding years of his life were spent in almost continual travel: over all parts of Great Britain, to North and South Russia, Siberia, the Kirghiz Steppes, Mexico, and the United States. It was on one of his annual visits to Colorado that he was seized with sudden sickness and died on September 21, 1878, at the early age of forty-five.

Thomas Belt was an accurate and intelligent observer possessed of the valuable faculty of wonder at whatever is new or strange or beautiful in nature, and the equally valuable habit of seeking a reason for all he saw. Having found or imagined one, he went on to make fresh observations, and sought out new facts to see how they accorded with his supposed cause of the phenomena. "The Naturalist in Nicaragua" has therefore a value and a charm quite independent of the particular district it describes. As a mere book of travel it is surpassed by scores of other works. The country and the people of Nicaragua are too much like other parts of tropical Spanish America, with their dull, lazy inhabitants, to possess any novelty. There is little in the book that can be called adventure, and still less of geographical discovery.