Hi Everybody,
'Fue' -- Thanks for your comments and good to have them.
At last I have a bit of time to resurrect this after my week away. So the feeling seems to be that mother and child are both alive but not necessarily fighting fit in the photo. There seems to be a division of opinion in the date, with I think more people going with the mid 1870s option. If this is so and assuming it is mum holding her own child and not another family member, then the lady is probably the first wife of Edward Rosthron and the child either Thomas born 1868 or Jane born 1870.
There were two further certificates waiting for me when I got home and they tell a sad story, as I thought they might. Edward Rosthorn's 1st wife (and possibly the lady in the photo) died on 1st January 1872, cause of death given as Child Bed 6 days, Peritonitis 4 days. Her baby, John, was born on 26th December 1871 and Edward registered the birth of his son and the death of his wife on the same day - 1st Jan, which was the day his wife was buried (according to newspaper obit.).
On 25th May 1872, the baby John died aged 5 months - cause of death, Debility. The informant was not the father, but an Esther Dawson, present at death. From the address of this Esther, and after a quick census search, it looks like the baby was 'farmed out' - I suppose Dad had to work with 2 small children to support. Initially I wondered whether the photo could be of this Esther Dawson and the baby, who died of Debility, could be John. But the child in the pic. is obviously much older than 5 months so it is cannot be them.
I don't think there is much more I can find out about the 1st wife, but I am glad through this thread to have found out about the baby who was born and died between the censuses and whom I never knew existed. It is good to have him named and his short story noted now.
I must now repeat a similar excercise with the 2nd wife, and as there is a gap between the children there is perhaps also another missing child.
Thanks for all your help and contributions everybody - its been fascinating.
Maggie