In 1808 he married Mary Ann Gilbert, an heiress, of Eastbourne, in Sussex, whose family name he afterwards assumed, on account of the hereditary estates to which he became entitled through this marriage.
This lady was of a strong, determined character. On one occasion when riding she was thrown, and dislocated her shoulder. Laying hold of her hunting-crop with both hands, she threw herself back and so brought the joint back into its place.
Once she had a dispute with some farmers, who would not continue their farms without a great reduction of rent. "Very well," said she; "then I will farm them myself." And she did so, and made them pay. She was the first in England to introduce the allotment system on a farm of hers at Eastbourne, Sussex. The marriage was due to Mr. Giddy meeting her when she was staying with her mother on a visit to Mr. Fry at Penzance.
She was a handsome woman, with a determined face, and she suited her husband admirably, for she was interested in many of the subjects that he took up. She was an authoress, moreover—she wrote upon "Tanks," "On an Improved Mode of Forming Water Tanks," "On the Construction of Tanks," in 1836, 1838, and 1840. Also "On the Self-supporting Reading, Writing, and Agricultural School at Willingdon, in Sussex," 1842.
On the death of Sir Joseph Banks the unanimous voice of the Royal Society called Sir Humphry Davy to the chair, and at the same time Davies Gilbert—as he now was—was nominated Treasurer under the man whom he had first helped to start in his career. Ill-health having obliged Sir Humphry Davy to quit England in the early part of 1827, Mr. Gilbert occupied the chair as Vice-President, and when finally Sir Humphry retired in the same year he was chosen President.
At that time a President was elected for life, but Davies Gilbert considered this to be unadvisable, and urged that the election should be for a term only; and his recommendation was accepted after a few years, when the presidency was required for the Duke of Sussex; thereupon it was hinted to him that he should act upon his expressed opinion and leave the chair for His Royal Highness. This he did without reluctance.
On his wife's estate in Sussex he introduced the Cornish stiles, of gridiron fashion—strips of stone laid down with an interval between each—and this prevents horses, donkeys, and cattle from adventuring to cross them. But the Sussex people on the Eastbourne estate revolted, and declared that they would not break their legs to please any Cornish Giddy or Sussex Gilbert, and he was constrained to remove them all.
He was a man of a versatile mind. He published, with a translation by J. Keigwin and W. Jordan, the early Cornish mystery plays of Mount Calvary and the Creation of the World.
He also undertook a Parochial History of Cornwall, giving first Hals' account from his MS., now in the British Museum, with additions from Tonkin, and a geological account of each parish by Dr. Boase, of no great value, and his own additions. This was published in five volumes in 1838.
He wrote also on steam-engines, on the employment of sea salt as a manure, on the improvement of wheels and springs for carriages, on the Eikon Basilike. He translated the Liturgy into Greek. Chambers in his Journal, Vol. II, 1844, has an account of the improvements effected on his wife's estate at Eastbourne.