I am intrigued to find out why the Adamthwaites had disappeared from Adamthwaite farm, and indeed from Ravenstonedale, by the late 1700s.  As part of a research project I have studied all the surnames of Ravenstonedale and it is clear that many of the holders of the commonest surnames (and Adamthwaite was the ninth most common surname in the parish in the 16th century)  started to drift away from the parish at this time.

This is contrary to the general pattern of surname migration, as the experts nowadays are confident that the highest densities of a particular surname in early 19th century records are the best clue as to a surname's origins (this rule does not include the commonest surnames which generally have multiple places of origin).

We know that during the 19th century, as the Industrial Revolution took hold, many families left their agricultural roots to seek employment in the cities - but generally some family members remained.  

The inheritance 'rules' laid down in the Ravenstonedale Customaries described in The Great End Book (which I am still in the process of transcribing) will certainly have led to many younger sons leaving the parish in order to seek employment if they were not required to help on the family farm - but at times whole families seem to have left the Dale.  

I hope that some of the research on general patterns of migration which I will be undertaking for all families in Ravenstonedale as part of the Ravenstonedale DNA Project, may indicate whether the Adamthwaites were just following a common pattern. If you have any theories, I would be delighted to hear more.