Patrick Walsh Mallon M.R.C.S., Edinburgh, was in Maitland at least as early as June 1834 . He was acquainted with Dr. Thomas Parmeter and was referred to by Parmeter as that clever Irish surgeon. They spent an hour together at the Maitland races in 1835.
He married Catherine, the daughter of Samuel Graves Irwin R.N., Esq., of Maitland, on 26th January 1836.
PLANS FOR A HOSPITAL
In June 1839 he briefly entered into a partnership with Joshua Dowe. They were planning to equip a small hospital for the reception of patients, however this seems not to have eventuated. James Cochrane had established a private hospital at Maitland in 1839, however the earliest hospital in Maitland dates back 1832 when William Colman established a facility to treat convict servants.
Patrick Mallon gave a lecture on chemistry at Maitland in August 1840 which was later reported on....Considering the shortness of the notice previous to the lecture the church was numerously attended on the occasion. The lecture was very successful although deficient of some apparatus, which was not obtainable in Sydney. 
On 20th May 1840, Patrick Mallon was granted two acres of land at Maitland which had been promised to the late William Aird in 1830.
In 1842 he was granted 40 acres at West Maitland originally granted to Johnson Brothers....the said Patrick Walsh Mallon and his heirs in trust for Alexander Walsh of West Maitland, settler, Richard Stark of West Maitland, baker; Elizabeth Wall of East Maitland and Samuel Graves Irvin of West Maitland, gentleman; George Poulton of West Maitland as trust for John Duncan of West Maitland Carpenter; William Twiss Forster of Upper Williams River settler; the Rev. John Thomas Lynch of Maitland; Edward Jennings in trust for John Jennings of Swan Reach, settler; George Glew of West Maitland butcher; James Horton of West Maitland, settler and William Stirling of West Maitland settler and their respective heirs according to their respective right and interest. 
PLANS TO LEAVE MAITLAND
Patrick Mallon intended to leave Maitland for his native land in February 1841. He planned to sell all his properties and belongings in an auction to be held on 15 March 1841...... Dr. Mallon's lucrative Rent Roll of upwards of £500 per annum including Ranfurly Terrace and the remainder of his eligibly situated property at Port and West Maitland...altogether there were 13 properties including cottages let to Mrs. Liddle and a brick built and beautifully finished residence let to the Rev. Mr. Lynch; a brick Surgeon's residence let at £60 per annum; and seven slabbed houses. 
He may not have returned to Ireland as in June 1841 he attended the first annual meeting of the Society of Saint Patrick in Castlereagh Street Sydney. 
In January 1842 he was advertising to sell the lease of a small farm near Maitland. Later in 1842 he was again advertising to rent out properties in Ranfurly Terrace.
In 1843 he fell victim to the financial depression. He became bankrupt and by May 1843 had lost all but his wearing apparel, household furniture and surgical instruments. The 'Apothecaries Hall' in West Maitland owned by Mallon was advertised for sale by public auction in July 1843. The sale included the entire stock of drugs together with fixtures, bottles etc.
In 1870s a resident of Maitland looked back on the township as it was in the 1840's when the depression struck.....
Maitland's inhabitants were industrious and enterprising; many were rather more enterprising in fact than prudent. But in a newly founded township that, perhaps, is a failing which leans to virtue's side. People even then made haste to be rich, not by the slow humdrum process of labour and saving, but by sharp brilliant strokes of business. In 1842 and the following year an unnatural and inflated state of affairs which had previously existed collapsed throughout the colony, and no part of the country suffered more from the panic by which this false show of prosperity was everywhere annihilated than the district of Hunter River, just as in no other part of the country had the sham, while it lasted, attained such enormous dimensions. The credit of West Maitland-even then the chief emporium of the northern districts -fell very low. But the rich natural resources of the Hunter district soon enabled the in habitants to hold up their heads again, and after a little while everything went ahead, if not so fast as before, yet at a safer rate of progression 
Patrick Walsh Mallon's wife Catherine died in 1845 after giving birth to a daughter. In August 1849 he moved to Moreton Bay where he took over the duties of Dr. Ballow at the quarantine station for two years.
He returned to Sydney in 1851, later taking up a practice at Dungog. In 1854 he married Angelina Harrison.  In that same year there is a record of a marriage to Elizabeth Wright at Dungog. Together Patrick and Elizabeth had children Olivia b. 1855; Jane b. 1856 d. 1857 and Patrick L. b. 1857 at Dungog.
Patrick Walsh Mallon died at his residence Mount Edgecombe, Camperdown, Sydney on 6 April 1883 age 76 years.
NOTES AND LINKS
1). Dr. Patrick Malone attended Sophie Wadsworth in Maitland in 1835 after she had been raped by four men (Sydney Gazette 12 February 1835). ? Patrick Walsh Mallon.
2). Mallon v. Meehan - Plaintiff a surgeon living at Brisbane. Defendant innkeeper at Drayton, Darling Downs. Dr. Mallon claimed 40 pounds for medical expenses Sydney Morning Herald 16 September 1851
 The Sydney Herald (NSW : 1831 - 1842) Thu 19 Jun 1834
 State Records of NSW; Registers of Land Grants and Leases; Series: NRS 13836; Item: 7/461; Reel: 2549. Source Information: Ancestry.com. New South Wales, Australia, Registers of Land Grants and Leases, 1792-1867
 State Records Authority of New South Wales; Registers of Land Grants and Leases; Series: NRS 13836; Item: 7/461; Reel: 2549. Source Information: Ancestry.com. New South Wales, Australia, Registers of Land Grants and Leases, 1792-1867
 Australasian Chronicle 29 August 1840
 Australasian Chronicle 4 March 1841.
 Australasian Chronicle 17 June 1841
 Maitland Mercury 25 January 1854
 Australian Town and Country Journal (Sydney, NSW : 1870 - 1907) Sat 16 Dec 1871