Abstract :
Although I was not able to read the paper before the Luton Section, owing to the short notice, I have been asked to reply to one or two points that arose in the discussion. In the first place I would like to say that Mr. Bedford, who was in the chair, answered quite a number of the points that I would, had I read the paper, have normally have had to answer, and it is astonishing to find how near in his answers he has come to my idea of what those answers should have been. I want to place it on record how much I appreciate Mr. Bedford´s efforts in this direction. With regard to the discussion as a whole, I think it will serve a useful purpose, but I do not propose to go over the discussion in its entirety but
