Name: James Mather 
Gender: Male 
baptism/christening date: 02 Nov 1761 
baptism/christening place: BANK STREET UNITARIAN OR PRESBYTERIAN,BOLTON LE MOORS,LANCASHIRE,ENGLAND 
birth date: 28 Sep 1761 
father's name: Richard Mather 
mother's name: Anne 
indexing project (batch) number: C08640-1 
system origin: England-ODM 
source film number: 0560877 (RG4 64, 2004) 
    Abode: Turton
    Notes: Baptised at Bolton
    Baptised by: Revd. Philip Holland
This is the most likely, as future wife Happy Lomax was also Christened at Bank Street Unitarian. Although the James and Susannah baptisms dont align with the others, there is only one James and Ann family in Bolton district, so it seems Isaac was baptised late (after the marriage).

or

JAS. MATHER
Birth: 
Christening:  11 DEC 1763   Saint Peter, Bolton Le Moors, Lancashire, England
Parents:
  Father:  ELIAS MATHER
  Mother:  MARY

or

James Mather
Christening:  15 JAN 1769   Deane, Lancashire, England
Parents:
  Father:  James Mather

May have died between 1798 and 1815, as Happy married again in 1816.  Most probably about 1814, but its a guess!

Several death records for James Mather, but none match age and spouse.

A James Mather Cash receipt for £2-2-0 for a grave no. 7-29 is recorded in 20-Oct-1811 in the Register of Burials at Bridge Street Wesleyan Chapel at Little Bolton in the parish of Bolton le Moors, Lancashire from 1810 to 1837.

Non-Conformist Record Indexes (RG4-8),
Name: James Mather 
Event Type: Burial 
Burial Date: 20 Oct 1811 
Burial Place: Bolton Le Moors, Lancashire 
Affiliate Publication Number: RG4_1024 

Happy Mather is listed in the L.B. Poor Book for 1811, which is consistant with Samuel dying in 1811.  She was a rate and tax payer, with 2s 9d rate collected for a House in Blackburn Street and not on the poor recipient list.

There is another burial record for a James Mather, 54 in Wigan 28 June 1814, but the Bolton record is more likely.

Betty was 20 when she died, so born first half of 1769

Name    Betty Lyon
Mother    Jane Lyon
Father    John Lyon
Baptism    12/1769 Wigan Lancashire England
Vital    12/1769 Wigan Lancashire England

Name:    Betty Lyon
Event Type:    Christening (Baptism)
Baptism Date:    31 Dec 1769
Baptism Place:    Wigan, All Saints, Lancashire, England
Father:    John Lyon
Mother:    Jane Lyon

Betty, daughter of John & Jane Lyon of Market Street.

Betty Mather died in August, wife of James, aged 20, probably after childbirth of Nancy. Nancy dau of James and Elizabeth was baptised in September 1789

Burial: 5 Aug 1789 St Peter, Bolton, Lancashire, England
Betty Mather - Wife of James Mather of G.B.
    Age: 20
    Abode: GB
    Source: LDS Family Search

Name:    Betty Mather
Death Age:    20
Event Type:    Burial
Birth Date:    abt 1769
Burial Date:    5 Aug 1789
Burial Place:    Bolton-le-Moors, St Peter, Lancashire, England
Spouse:    James Mather
Reference Number:    L243/1/2/2

NAME:     James Mather
MOTHER:     Betty Mather
FATHER:     James Mather
BAPTISM:     10 Apr 1785 - Bolton le Moors, St Peter, Lancashire, England
Abode: G.B

James was baptised with John, son of John and Margaret Maken.

This James is baptised April before his parents were married in Sep 1785.

There is another James son of James and Betty Knowles baptised 15  Jan 1875 at Walmsley. The mother was names, so this James can not be the son of Bertty Knowles, and there is only one other James & Betty marriage.

Name: Elizabeth Mather 
Gender: Female 
Christening Date: 05 Oct 1788 
Christening Place: Lancashire, England 
Birthplace: GB 
Father's Name: James Mather 
Mother's Name: Betty Mather 
Indexing Project (Batch) Number: C03934-6 
System Origin: England-EASy 
GS Film number: 1966744 
Reference ID: item 2 Bolton Oct 1788 

Elizabeth D. of James & Betty Mather of G.B. 5 Oct 1788

There is no infant or child death of an "Elizabeth" mather, and the one for "Betty" is his wife.

Name:    Betty Mathar
Burial Date:    5 Aug 1789
Parish:    Bolton-le-Moors, Lancashire, England
Father's name:    James Mathar
Register Type:    Bishops Transcripts
Reference Number:    Drm/2/19b
Text: Betty W of James Mather of G.B.".