Summerhill - I was looking at Magilligan RC records today in PRONI and noted your Cummings family mentioned. The name was originally Miskimmins and also McCummins in the earlier records and most of the family in the Magilligan/Aghanloo area were Presbyterian. In the absence of formal census material then the church registers are very important in building up a picture of the family - sponsors, witnesses & addresses etc:
You probably have these details already [these are all of the Cummings entries in the Magilligan RC records]
Magilligan RC registers: c. 1863-1880 MIC 1D/56/1
Marriages [the RC registers did not name father but from civil marriage all of these Cummings are children of James Cummings]
Married 22 Aug 1871 James Cummings of Ballycarton to Elizabeth McDermott: Witnesses - Daniel Cummings, Ballycarton & Jane McDermott, Duncrun
Married 27 Sept 1874 Daniel Cummings to Margaret Mullan: Witnesses - Jas & Mgt McLaughlin of Clagan
Married 3 Feb 1877 John Coghlan Ballycarton to Elizabeth Cummings, Ballycarton: Witnesses - Edward Mullan and Annie Cummings, Ballycarton.
Baptisms
25 Sept 1865 Elizabeth of Samuel Cummings & Mary Ann Coyle, Ballyhendry: sponsors - John Mooney, Ballyhendry & Nancy Cummings of Ballycarton.
[Note - this is the only entry for children of Samuel Cummings. It seems he was related to the Ballycarton Cummings'].
19 May 1872 Mary Ann of Daniel McLaughlin & Elizabeth Cummings Ballycarton: Sponsors - Pat McIvor & Mary Ann Given [note in margin - Mary Ann married to Galloway in New York 5-11-1908]
18 Aug 1872 Sarah Jane of James Cummings and Elizabeth McDermott of Derry: Sponsors - Daniel Cummings Ballyc[faded] and Sarah Ann McDermott, Duncrun.
28 June 1874 Daniel of Daniel McLaughlin & Elizabeth Cumming, Ballycarton: Sponsors - John Coghlan & Elizabeth Cumming of Ballycarton.
10 Feb 1877 James of Daniel Cummings and Margaret Mullan, Ballycarton: Sponsors - John Coghlan & Mrs John Coghlan of Ballycarton
27 Aug 1876 Elizabeth of Daniel McLaughlin & Elizabeth Cummings of By'carton: Sponsors - Eliza Cummings & Pat McIvor
Burials [only one Cummings burial]
27 July 1875 - Mrs Cummings, Ballycarton
Note - on its own the burial seems to be virtually useless. However, this must be the mother of the Cummings' family above since the title 'Mrs' Cummings suggests so. A search of the civil death index for the year 1875 produces one hit -
Sarah Cummings died 1875 aged 62 years [born c.1813] Newtownlimavady, Volume 11 page 573.
[Sarah Cummings above could be the wife of James Cummings that you were looking for?].