“A more accurate and quantitative knowledge of that earth history which is now being recorded is needed in order to obtain in turn a more accurate knowledge of the past.” This statement, quoted from Professor Barrell,2 is important enough to be repeated and put in the form of an admonition to geologists which might be framed thus: “Know well the present before crossing the threshold of the past.” I have attempted in recent years, so far as circumstances and official duties would permit, to carry out in some measure the spirit of this admonition. Some of the scraps of information which I have gathered while trying to understand present-day processes in geology have a bearing on the subject which has been assigned me. These will be offered for your consideration frankly as fragmentary materials and suggestions for the precise definition of the criteria of marine clastics which will be written . . .