The year 1851 saw the completion of the Phycologia Britannica, and he at once set to work on his Nereis Boreali-Americana, published in three parts in the Smithsonian Contributions to Knowledge—a work of 550 quarto pages containing an account of all the known species of North American Algae, and 50 coloured plates, lithographed as usual with his own hand—a fine piece of work, and one which has not yet been superseded. This was a time of strenuous labour, for already he was planning a still more extended foreign tour; but he found time in the autumn of 1852 for a trip to Switzerland with Sir William Hooker and other friends.
In August, 1853, Harvey set out on the most extended scientific expedition of his life. So far his collecting had been done in Europe, South Africa, and North America. Now he was to visit the Indian Ocean and Australasia, and to investigate their seaweed flora, as yet but little known.
A short stay was made in Egypt, and a sea-shore ramble at Aden yielded Padina pavonia and a few other seaweeds, but otherwise he made no stop till Ceylon was reached. There he travelled a good deal, but seaweed collecting was not so successful as he had hoped. Some of the places explored proved unproductive, and the prevalence of the monsoon rendered collecting difficult or impossible. But the last three weeks, spent at Belligam Bay and Point de Galle, yielded excellent results, and he proceeded to Singapore en route for Albany, with a collection of about 5000 specimens of Algae.
The first work in Australia was done in the extreme south-west. Here he gathered seaweeds assiduously in King George's Sound, but the ground proved rather poor, though one welcome storm brought him a rich harvest, of which he preserved 700 specimens in one day. He moved on to Cape Riche, to the eastward, travelling through the bush on foot, and thus making intimate acquaintance with the interesting vegetation as well as the fauna of the district traversed. Cape Riche proved poor also, and he went northward to Perth, where he met James Drummond, the pioneer of West Australian botany, formerly of the Botanic Garden at Cork, and the discoverer of Spiranthes Romanzoffiana in the British Islands. At Perth he struck good ground. "This place is an excellent locality for Algae," he writes, "I am daily finding fresh ones, and have the prospect of a good harvest of novelty and interest.... The days are too short for my work. My best collections are made at Garden Island, nine miles distant. I have been twice landed for a two hours' walk, and on both occasions collected so much that it took three days to lay them on paper." Rottnest Island also proved highly productive, and he gives a very attractive picture of the great rock-pools on the limestone reefs, filled with brilliant seaweeds, many of them undescribed. Here he lived in the deserted convict establishment, and amassed a large and valuable collection.
Thence he went to Melbourne, where he collected at several points about Port Phillip, notably on Phillip Island; after which he sailed for Tasmania, where at Georgetown he had a month's successful work with the Rev. J. Fereday, himself an enthusiastic student of botany, seaweeds included. Passing through Hobart, he obtained permission to visit Port Arthur, at that time a great convict station, for which he sailed on March 1, 1855, passing the grand basaltic headlands of Cape Raoul and Cape Pillar. At Port Arthur amid exquisite natural surroundings marred by the presence of chained prisoners, armed warders, and sentry-lines of fierce dogs, he worked successfully, doing much shore-collecting, and dredging with the aid of a crew of convicts and armed guards. After a little rather unsuccessful collecting at Sydney and Newcastle he sailed for New Zealand, where he spent a few weeks at Auckland. While the terrestrial flora proved highly interesting to him, he found the shore poor in Algae; but he enlisted a useful recruit for collecting, in Mr Knight, Auditor-General, who undertook to collect and send him further material.
The 26th July, 1851, found him at Tonga Taboo, in the Friendly Islands, revelling in his first glimpse of nature in mid-Pacific. The fringing reef proved somewhat disappointing, for amid the multitudinous and many-coloured animal forms only a few green Algae were to be found. Harvey spent six months in the Pacific, visiting island after island according as the mission boats supplied a means of transport, collecting seaweeds and a good many marine animals. At that time social conditions in the South Seas were very different from what they are now. The adjoining Fiji Island group, for instance, was still in a savage state: the captain of the mission vessel told Harvey how, only four years before, he had seen one hundred human bodies laid out for a great feast, and cannibalism was still a habitual practice there; but the Friendly Islands, though but recently in a similar condition, seem already to have deserved their name, and Harvey's experiences of the natives, with whom he was much in contact, appear to have been of the pleasantest description; in Fiji also, where several weeks were spent, the founding of a Christian mission (permitted only two years before after eighteen years' refusal) had already greatly altered local practices; devil-worship and cannibalism were rapidly dying out. Harvey, applying at the mission station for a responsible guide, was furnished with a man entitled "Koroe," which, it appeared, was an honourable title "something equivalent to a C.B. in England," and bestowed only on a person who had committed at least five murders. Harvey returned to Sydney, and thence to Europe by Valparaiso and Panama, having a severe bout of fever on the way. He reached home in October, 1856, after an absence of over three years.
Here an important change of life awaited him. G. J. Allman succeeded to the Natural History chair in Edinburgh, rendered vacant by the death of Edward Forbes, and Harvey was elected to the chair in Trinity College, Dublin, the difficulties which led to his rejection twelve years earlier being not raised on this occasion, though the law remained the same. At the same time, the incorporation of the several Dublin Society professorships in the newly founded Museum of Irish Industry (now the Royal College of Science for Ireland), gave him additional work, as his post was converted into a Natural History and Economic chair. However, the considerable increase of lecturing and teaching thus brought upon him did not prevent his pushing on vigorously with the now large arrears of phycological work. His first action was to finish and publish the third and last section of the Nereis Boreali-Americana and then bring to a conclusion his enumeration of the seaweed flora of North America. This was accomplished in 1858, and in the same year he began the publication of the results of his work in Australia. The Phycologia Australica, which was issued in parts during the ensuing five years, ran to five volumes, each containing sixty coloured plates, and descriptions of all the species known from Australasian waters. In the year following the launching of this work, he commenced the publication of two important treatises on the phanerogamic flora of South Africa. In the first of these, the well-known Flora Capensis, he had the co-operation of Dr O. W. Sonder of Hamburg. This extensive work he did not live to complete; the third volume, which ran as far as the end of the Campanulaceae, being published the year before his death. The other work was his Thesaurus Capensis, a series of plates of rare or interesting South African plants, designed to supplement and illustrate the unillustrated Flora; of this he lived to issue only two volumes, each containing one hundred plates.
Harvey's home life, which for several years had been very lonely, was transformed in 1861, when, at the age of fifty, he was married to Miss Phelps of Limerick, whom he had long known. But almost immediately afterwards the shadow of death appeared, haemorrhage from the lungs warning him that his newly found happiness might not endure. After a summer spent at his favourite Miltown Malbay, on the wild coast of Clare, he was able to resume his college duties and his work on Flora Capensis. Although he never fully recovered his health, he laboured diligently at the works he had in hand. He had a noble example of continued devotion to science in his old friend Sir William Hooker, whom he again visited, on returning from a tour on the Continent, in the autumn of 1863, to find him, in his seventy-ninth year, finishing off the last volume of his Species Filicum, and "already beginning to nibble at another book." This was a further work on ferns, the Synopsis Filicum, on which Hooker was busily engaged until within a few days of his death in the summer of 1865; it was completed by J. G. Baker and published three years later. During the winter of 1865, Harvey himself became seriously ill, and, an immediate change to a mild climate being recommended, he and his wife went to stay at Torquay with Lady Hooker, and there he died on 15th May, 1866.
Harvey was only fifty-five years of age when he died, but he had won for himself a foremost place among systematic botanists. Life, as Lubbock has said, is measured by thought and action, not by time; and according to this standard, Harvey's life-cup was already full and running over. He had used to the utmost the gifts which he possessed. The capital with which he entered on his career comprised a critical eye, a deft hand, and that scientific enthusiasm without which no botanist ever travels far. On the other side of the account, he had two serious deterrents, a rather delicate body, and a complete absence of scientific training. "Apropos of dissection," he writes to Hooker in his younger days, "I am a miserable manipulator, and should be very grateful for a few lessons." From the beginning he had a shrewd perception of what lay within his reach, and what was beyond it. "The extent to which I mean to go in botany," he wrote at twenty-one years, "is to know British plants of all kinds as well as possible; to know Algae of all countries specially well; to collect all foreign Cryptogamia that may fall in my way, and to know them moderately well.... My reason for choosing the Algae is pure compassion; they being sadly neglected by the present generation, though at a former time they were in high favour."
In the letters written even in boyhood we see foreshadowed the direction and extent of his future researches. "Exactly what he determined in youth to accomplish," says Dr John Todhunter in his Preface to Harvey's Memoir, "he accomplished; the work which he took upon himself to do he did, honestly and thoroughly; the fame which he desired to achieve, he achieved." He saw that his strength lay in discrimination, description, and illustration, and to these—the necessary census task which forms the groundwork on which great theories may be built up—he confined himself.