WILLIAM HENRY CAVENDISH, third duke of Portland, was born on the 14th of April 1738. Having finished his education at Christ Church, Oxford, he went on his travels. Soon after his return he was elected for the borough of Weobly, in the first parliament of the king's reign. For this borough, however, he did not sit long; for, on the death of his father, on the 1st of May 1762, he was called up to the house of peers. He immediately joined the opposition; and, in 1763, his name is found among the minority against the cider bill, and along with that of the duke of Grafton in a protest against it. The next session he also signed a protest on the motion to vote away the privilege claimed by members of parliament in matters of libel. In 1765, when his friend the marquis of Rockingham came into power, he was appointed lord chamberlain, and he retired when the marquis went out of office. In 1768 there was a violent contest for the county of Cumberland; and as the duke warmly supported the two opposition candidates, the ministry, in order to weaken his influence, and at the same time to increase that of Sir James Lowther, who was one of the ministerial candidates, granted to the latter Inglewood forest, an extensive and valuable estate, which had been granted by King William III. to the first duke of Portland, and had remained in possession of that family ever since. The new grant was made in consequence of a report from the surveyor-gen- ral of crown lands, that the premises were not comprised in the original grant from King William to the duke of Portland, but were still vested in the crown. A letter was written from the treasury, directing the duke to prepare his title, and assuring him that nothing should be decided concerning the grant till such title had been stated and maturely considered: but while his grace's agents were busily employed in their researches and inquiries, he received a second letter, informing him that the grants were passed and the leases signed. A caveat had been entered at the exchequer to stop the progress of the grant; but when Lord North was prayed to withhold affixing the exchequer seal, he replied that, as chancellor of the exchequer, he was bound to obey the orders of the treasury.

On the 19th of November 1771 this great cause was tried before the barons of the exchequer in Westminster Hall. The court recited all the records and prerogatives of the crown, from Edward I. to the lease made to Sir James Lowther; when, after a full and impartial examination of the said lease, it was found invalid, agreeably to the statute of the 1st of Anne, which expressly requires that, upon every grant from the crown, there shall be a reserved rent, not under the third part of the clear yearly value of the manors, lands, &c. as shall be contained in the grant. Sir James Lowther's grant from the crown, being only a quit-rent of 13s. 4d. for the whole of Inglewood forest, was immediately determined by the court an inadequate third proportion, and he was nonsuited accordingly. The nul-lum tempus bill, or the act for quieting the possessions of the subject against all pretences of concealment whatsoever, which was brought into parliament in 1768, and passed in the following year, owed its rise to this grant of the Portland property to Sir James Lowther.

In 1766 the duke of Portland had been bound more closely than ever to the Rockingham party, in consequence of his marriage with Lady Dorothy Cavendish, sister to the duke of Devonshire. On the resignation of Lord North he was appointed lord-lieutenant of Ireland; and during his government the parliament of that country was declared independent of the British parliament. After an administration of somewhat more than three months he was recalled, when Lord Shelburne came into power. On the death of the marquis of Rockingham he was recommended by the privy council to the king as his successor at the Treasury; but Lord Shelburne was preferred. When the coalition came into power, however, he obtained the situation of prime minister, and went out of office with them. During Mr Pitt's difficulties, when he first came into administration, in consequence of the house of commons being against him, an attempt was made to form a coalition between him and the duke of Portland; but his grace objected to the conditions on which Mr Pitt came into power, and refused his support unless he would resign his place and come in again on equal terms with himself and his friends.

In 1792 he was elected chancellor of the university of Oxford; and soon afterwards he, as well as several other friends of Mr Fox, who differed from that statesman respecting the French revolution, left the opposition and joined the ministry. Upon this he was appointed lord-lieutenant of the county of Nottingham, and, in 1794, secretary of state for the home department. The scarcity and high price of provisions, and the state-trials, which occurred soon after he became secretary of state, rendered his office arduous and unpleasant. He discharged his duty, however, under these circumstances, with moderation, and with acknowledged good intentions, though not always perhaps with vigour and judgment. He continued secretary of state till Mr Addington became prime minister in 1801, when he exchanged this situation for the more easy duty of president of the council. On the death of Mr Pitt, and the appointment of Lord Grenville and Mr Fox to the ministry, in the spring of 1806, he was removed from the presidency of the council; but he was again called into public life, and placed at the head of the treasury, in March 1807, when Lord Grenville's administration closed. His Grace, however, though nominally the prime minister, was too infirm to take an active part in the high and arduous duties of this situation, which were discharged almost entirely by Mr Perceval, the chancellor of the exchequer. He continued nominally the first lord of the treasury till a very short time before his death, which happened on the 30th of October 1809.

The abilities of his grace were certainly but moderate, and very far inferior to those which he must have possessed had he been, as latterly there has been an attempt to prove, the author of Junius's Letters; but his understanding was good, and he was by no means unwilling or unable to give regular attention to official business. His political integrity was never questioned, even by the party he abandoned.