There are a few possibilities for this entry. On 21 March 1818 an advert in the Morning Chronicle, under the heading ‘Books Published this Day’ reads: ‘in 8 vo. Price 4s. CHILD HAROLD’S PILGRIMAGE to the DEAD SEA; Death on the Pale Horse: and other Poems. Printed for Baldwin, Cradock, and Joy, Paternoster-row.' Earlier that year, Mr Carey had published a Critical Description of Mr. West's Death on the Pale Horse which had, according to The Times caused an 'uncommon sensation in the amateur circles'. Alternatively, Godwin could be referring to an exhibition. The biblical subject of death on a pale horse became popular around the time of Godwin's entry and reflected the taste for apocalyptic scenes:

And when he had opened the fourth seal, I heard the voice of the fourth beast say, Come and see. And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.

The Revelation of St John the Divine, Chapter 6, verses 1-8.

Artists John Hamilton Mortimer (1740–1779), Benjamin West (1738–1820), William Blake (1757–1827), and Philippe Jacques de Loutherbourg (1740–1812) all painted a version, and in a caricatured version by James Gillray (1756–1815), Pitt is seen riding a white horse, political followers in his wake. For descriptions of some of the most popular images following Mortimer, and the social milieu from which they arose, see the online catalogue for Tate Britain’s Gothic Nightmares exhibition (2006).

The Times advertised a ‘MECHANICAL and PICTURESQUE Theatre of Arts’ after de Loutherbourg. However, the opening of the exhibition is listed for the following Sunday. On the 26th October (six months after Godwin’s entry) the Morning Chronicle printed an advert for ‘Mr. West’s Exhibition. – The great Picture of Death on the Pale Horse, Christ Rejected, St Peter’s First Sermon, with several other Pictures and Sketches from other Scriptural Subjects are now exhibiting…at Pall-mall’.

See also DNB.