During the period 1942 to 1945 D Dylan Pritchard MA FSS of the University of Wales at Bangor wrote a number of articles on the Welsh slate industry for Quarry Managers' Journal (QMJ). 

I am grateful to the publishers for permission to reproduce the articles here. Information about Quarry Management, the successor to QMJ, can be found here.

Dylan Pritchard's Master's thesis, The slate industry of North Wales: a study of the changes in economic organisation from 1780 to the present day is held in Bangor University library. (1935:8)

Other records of his work held at the university library include:

1. Historical aspects of the Welsh slate industry QMJ 1942 - 1945 (X/KF 1935PRI);
   

2. The slate industry of North Wales: Statement of the case for a plan (X/KF 189PRI);
   

3. The economic condition of the Nantlle valley 1945 (X/KF 189PRI).
   

Some of the tables are difficult to see. There are links to larger views.