The Neptune was built at Cheptow in 1836.  This was her only voyage transporting convicts to Australia. She was the next convict ship to leave Ireland for New South Wales after the departure of the Sir Charles Forbes two weeks previously.
The Convicts of the Neptune were tried in counties and cities in Ireland - Antrim, Limerick, Carlow, Dublin, Tipperary, Longford, Waterford, Galway, Wicklow, Kildare, Kerry, Mayo, Westmeath, Tyrone, Meath, Armagh, Cork, Londonderry, Donegal, Kings Co., Mayo, Down, Fermanagh, Donegal, Clare, Antrim, Queens Co., and Clare. Their crimes were mostly various forms of theft and robbery as well as murder, pledging, bigamy, manslaughter, sacrilege, assault, embezzlement, perjury, rape and having base coin or forged notes in their possession. There were several sent for white boy crimes and two former soldiers court-martialed for desertion or mutiny.
Military Guard and Passengers
Passengers included Major Elliot, Mrs. Elliot and child, Lieut. Baker and 28 rank and file of 51st regiment, 6 women and 8 children.
This was the first detachment of the 51st regiment to arrived. They were to replace the 21st regiment at Hobart 
The Neptune sailed from Dublin on 27th August 1837.
Surgeon Patrick Martyn
This was Patrick Martyn's only voyage as surgeon superintendent on a convict ship. He was approximately 34 years of age in 1838. The Medical Journal for this voyage is not available. Find out more about Patrick Martyn here.
One hundred and ninety-seven male prisoners arrived in Port Jackson on 2 January 1838 three having died on the passage out - Michael Enright Connor, Michael Kennedy and Daniel Leehane
Notes from the Indents
The convict indents include name, age, education, religion, marital status, family, native place, trade, offence, place and date of trial, sentence, former convictions and physical description. Also included are occasional notes re relatives already in the colony and pardons. There is no indication where the convicts were assigned on arrival. The following notes are extracted from the indents:
James Behan - Uncle Patrick Behan, a prisoner 13 years in the colony
John Benson - Three first cousins, Mary, Biddy and Patrick Benson, came prisoners seven years previously.
Michael Brennan - Brother and sister Denis and Mary Brennan, both prisoners out about two years. Michael was later sent to Norfolk Island.
Henry Canavan - Relative James Cannavan came a prisoner 12 months previously
Joseph Clayton - First cousin Samuel Clayton, engraver came free to the colony.
Bernard Coyle - First cousin, Terence McIlhone came out as a prisoner
Daniel Devine - First cousin Patrick Devine, a prisoner, arrived in 1837 for life.
Thomas Grady - Wife Margaret Grady, a prisoner per Sir Charles Forbes
Henry Greene - First cousin to George McCormick, prisoner on board
John Harrold - Ann Devine a prisoner came about 11 years previously
John Hayes - John Kelly, a prisoner came about 3 years previously
Patrick Hayes - Aunt Mary Hayes came free but since transported
James Hetherington - First cousin William Edge, a prisoner came 8 years previously
John Higgins - Brother a prisoner per Calcutta 1837
Michael Hogan (age 13) - Parents Thomas and Margaret Hogan came prisoners two years previously per Thomas Harrison
Michael Hogan - First cousin John Gleeson came a prisoner 3 years previously
Thomas Hogan - Stepbrother James Sporesea, bricklayer came prisoners 2 years previously
James Kavenagh - Brother Charles Kavenagh, a prisoner came out previous March
Patrick Kelly - Brother in law John McGrath came a prisoner 8 years previously
Timothy Kennedy - Brother John Kennedy a private in the 28th regt
George McCormick, - Brother Andrew McCormick, a prisoner came out 18 months previously. Cousin to Henry Greene, prisoner on board
Richard Magarry - Brother John Magarry, a prisoner came 6 years previously
Martin Maguire - Brother Patrick Maguire, prisoner for life arrived per Calcutta 1837
Francis Pearson - Brother Michael Pearson, prisoner, came 13 years previously
William Rowley - Brother Samuel Rowley, prisoner per Recovery 1836
James Ryan - Father, William Ryan a prisoner 18 months previously. Brother to Jeremiah Ryan, prisoner on board
Jeremiah Ryan - Father Ryan, brother Barnaby Ryan, both prisoners out about 2 years previously.
Martin Shanahan - First cousin James Shannahan, a prisoner came 12 months previously
Luke Shanley - Brother James shanley a prisoner 18 years ago
Timothy Shehan - Uncle Patrick Shehan came a prisoner 6 years ago
Richard Stephens - Cousin John Stephens, a prison 12 months previously. 
2). An accident which had nearly been attended with fatal consequences occurred off the inner point of Mrs. Macquarie's Chair on Saturday afternoon. Mr. Mackay, of Darlinghurst, and Mr. Abercrombie, of the Glenmore Distillery, had been on board the ship Neptune, lying off Dawes' Battery, and were, at the time of the accident, returning to Mr. Mackay's residence, accompanied by Captain Nagle of the Neptune, in the ship's cutter, with four of the seamen.
When off Mrs. Macquarie's Chair, at about 100 yards distance from the land, and in the act of tacking, a sudden gust of wind caught the sails and upset the cutter, and the whole of the people on board were precipitated into the water. Mr. Mackay, who is considerably advanced in years, and was at the time in a very indifferent state of health, made towards the shore, as did several of the younger and stronger of his companions. Before he could accomplish his object his strength failed him and he sank to the bottom, where he must have perished but for the prompt aid afforded him by Captain Nagle and two of the seamen who swam to his assistance and brought him safely, though senseless to shore. Mr. Abercrombie and two of the seamen saved themselves by clinging to the boat. - Sydney Gazette 16th January 1838
3). The Neptune was to depart Sydney for Valparaiso via the Bay of Islands in February 1838.......
We have been favoured with an original letter written in the New Zealand language, by a chief at Coromandel Harbour, addressed to Captain Nagle of the Ship Neptune, in March, 1838. The following is a literal translation : -
'Friend Captain Nagle, bring me from England a pair of very large thick blankets and likewise a double-barrel gun; bring plenty of them, friend; be quick, and come; do not deceive us; and friend, be certain and come here and do not be long, and bring our child [home; and iriend do not be long and bring us plenty of casks of tobacco to buy land for yourself. 'Coromandel Harbour, New Zealand, Na Puiiata. March 27th, 1838.' - Information Relative to New Zealand: Compiled for the Use of Colonists
 Bateson, Charles Library of Australian History (1983). The convict ships, 1787-1868 (Australian ed). Library of Australian History, Sydney : pp.354-355, 390