"My specimen," he writes, "was picked up by a lady who accidentally landed for a few hours in a little harbour, into which the ship put during a gale, and she describes the shore as covered with the most wonderful profusion of plants and animals. She got all the pocket handkerchiefs of the party and filled them with what came first to hand, and in this hasty way picked up sixty different kinds of sponges, forty of which are new species, and several Algae, among which was the above described beauty. Her husband (a captain) is going out again, and promises to gather all he can meet with. Don't I hope he may have a run in again in a squall!"
Harvey now commenced the publication of the first of his larger works on seaweeds—the classical Phycologia Britannica, a series of 360 coloured quarto plates, drawn on stone by his own hand, representing all the species then known to inhabit the British Isles, and accompanied by suitable letterpress: the whole taking five years to complete. This work represented an immense advance in the knowledge of British sea-weeds, and, by the beauty and excellence of its plates, did much to popularize the study of these interesting plants.
In the following year he began his Nereis Australis, or Algae of the Southern Ocean. This was the first fruits of a comprehensive scheme of publication, which in its entirety was to "form a compendious picture of the vegetation of the ocean," the Nereis Australis being followed by a similar Nereis Tropica and Nereis Borealis; but only a section of the scheme was carried out, and publication stopped with the issue of 120 pages of letterpress and fifty coloured plates, drawn as usual by Harvey himself. In 1849 he issued The Sea-side Book, a popular account of the natural history of the sea-shore, which ran through several editions.
About this time he secured an additional appointment which, while it added to his professional duties, also increased his opportunities for research. The Royal Dublin Society, founded in 1731 for the improvement of husbandry, manufactures, and other useful arts and sciences, and aided by considerable government funds, had long since embarked on comprehensive schemes for the development of both science and art. To its activity is due the foundation and building up of many of the leading educational institutions in Dublin—the National Museum, the National Library, the Botanic Gardens at Glasnevin, the Metropolitan School of Art. The Society had established also professorships of zoology, botany, natural philosophy, chemistry, and so on. In 1848 the professorship of botany became vacant by the death of Dr Samuel Litton, and Harvey applied for the post. These appointments were made by the vote of the members at large, and strongly against his inclination, he had to enter on a personal canvass, of some experiences of which he gives a half humourous, half pathetic account in a letter to N. B. Ward, of "Wardian case" fame, who throughout life was one of his most regular correspondents. The issue was satisfactory, Harvey being elected by a three-fourths majority. This appointment placed him in control of the Glasnevin Botanic Gardens, of which Dr David Moore, so well known by his work on the Irish flora, was curator. It made him responsible besides for the delivery annually of courses of botanical lectures in Dublin, and also, at intervals, in selected towns in various parts of Ireland.
In the spring of 1849 Harvey accepted an invitation from the Smithsonian Institution and Harvard University to deliver twelve lectures on botany at the Lowell Institute at Boston, and others at Washington. The subject he chose for the Boston course was a comprehensive survey of the plant-world, from the point of view of the "progressive organization of the vegetable entity." The cryptogams had a place of honour, four lectures being devoted to Algae: it is interesting to note that the Fungi, which he designates "the most aristocratic of Crypts—fruges consumere nati," he placed immediately below the Flowering Plants, for reasons which, no doubt, he gave in his discourses. He sailed from Liverpool in July. Ocean traffic had been revolutionized since his last voyage from the Cape; instead of a dawdling sailing-ship, a steamer transported him in ten days to Nova Scotia; and with some of the old excitement with which he had started on his first climb up Table Mountain, he rambled away into the dark spruce woods, through the rich undergrowth of Kalmias, Ledums and Andromedas, with Sarracenias and Orchids rising from among the Sphagnums in the damper spots. He dredged and shore-collected also, but the seaweed flora was not rich. Thence he passed to New York, which he describes as like twenty Birkenheads and a dozen Liverpools, with slices from London and Paris, all huddled together, and painted bright red, with green windows. He visited Niagara and Quebec, and then travelled to Boston, where he was welcomed by Asa Gray, who was his host during his stay.
The lectures were well attended, and Harvey seems to have been satisfied with them and with the reception which they received; a popular lecture on seaweeds at the Franklin Institute at Providence was largely attended. These discourses, and the introductions and conversations that ensued, had more than a passing interest, as recruits were enrolled for alga-collecting, who subsequently supplied valuable material for his work on North American seaweeds. He saw all that was best of scientific society in Boston and New York, and met many of the great men of that generation—Agassiz, Bailey, Dana, Longfellow, Leidy, Pickering, Prescott, Silliman, Daniel Webster, Oliver Wendell Holmes. Having fulfilled his engagements and revisited the family of his late brother Jacob in New York, he turned his face southward in January for a collecting tour along the Atlantic sea-board.
After brief stays at Wilmington and Charleston, where he did a little botanizing, and sent to Kew a box-full of Dionaea, he arrived by boat at Key West one Sunday midnight in pouring rain, to spend the remaining hours of darkness in wandering about seeking a lodging. But by morning his fortunes had mended, and he spent a busy and pleasant month there, collecting by day, dodging mosquitos by night, and living mainly upon turtle and roast turkey, more ordinary foods being scarce. He made large collections of Algae, almost every day bringing to him new and beautiful forms. He had hoped to have the company of Prof. Bailey on this trip, but illness prevented this, and he had to carry out his work alone.
March saw him back in Charleston, where he attended the annual meeting of the American Association for the Advancement of Science. Then to Washington, where he delivered four lectures at the Smithsonian Institution. At Charleston he again met Agassiz, and once more records the profound impression which the American zoologist produced upon him. "His fine thought," he writes, "of reforming the classifications of animals by a more intimate study of their young in the various stages from embryonic life to full development, grows apace; and if he lives to bring out his conception of a system based upon this, it will not only crown his memory for ever, but be the greatest step of the present age in zoological science.... He is certainly a man of extraordinary genius, great energy, and with the most rapid inductive powers I have ever known. I could not help saying to myself, as I sat and listened, Well, it is pleasant to be hearing all this, as it is uttered, and for the first time. If one lives to be an old man, one will have to say, 'I remember to have heard Agassiz say so and so,' and then every one will listen, just as we should do to a person who had conversed with Linnaeus or Cuvier." We must remember that this appreciation of Agassiz's ideas was written nine years before the publication of Darwin's Origin of Species, and at a time when American men of science were much interested in a controversy as to whether mankind are all descended from Adam and Eve, or from several separate creations in different parts of the world. One of his last letters written on American soil contains a note on another subject, significant in the light of subsequent events. "I have been twice at sittings of the Senate, and have heard a good sensible speech on the Union question, which is now agitating folk here.... The bone of contention is Slavery."
The spring of 1850 saw him once again settled in Dublin, with a great accumulation of work on hand. Part of the summer was spent in collecting Algae on the coast of Antrim; and he met again his friends Asa Gray and his wife, who were visiting Europe. Another acquaintance made at this time, which ripened into a warm friendship, was the result of the finding by Mrs Alfred Gatty, well-known as a writer of fiction, of the Chrysymenia orcadensis of Harvey at Filey, in fruit for the first time—the examination of which convinced Harvey that the Orkney plant was only a variety of Chrysymenia rosea (Lomentaria rosea Thuret). Mrs Gatty became a useful ally in the collecting of seaweeds, and a valued friend; Harvey's influence is seen in her British Seaweeds, published in 1863.