Geologic literature abounds with statements relating to the occurrence of rain-drop impressions, but in few instances is information given as to the appearance of the marks which are so designated. When pitlike structures have been found, they have generally been ascribed to raindrops, and it has been concluded that the containing deposits were those of a region over which at times there was no water. Notes of caution have occasionally appeared, but they do not appear to have been widely read.2
The best paper on the subject of rain-drop impressions with which the writer is familiar is that of Lyell, in which are described “rain-marks of the Recent, Triassic, and Carboniferous periods.”3 This paper describes recent and fossil rain-drop impressions and gives some criteria by which they may be recognized. Some data are also given on impressions from the Triassic rocks of the Newark series, which are ascribed to . . .