TEEKANES. 



95 



(15) Rill-marks (Fig. 67) are still clearer evidence of a beacli-niade 

 deposit; they are the little furrowings made by the rills that flow down a 

 beach as the waters of a wave or tide retreat, and which become apparent 

 especially where a pebble or shell lies, the rising of the water upon the 



66. 



pebble causing a little plunge over it and a slight gullying of the surface for 

 a short distance below. The figure is from a slab of thinly laminated sand- 

 stone of the Medina formation, New York, as described and figured by 

 James Hall. 



(16) Rain-prints or rain-drop impressions are indications, like mud- 

 cracks, of exposure above the water level at low tide, or at least a low stage 

 of the waters, when the bed of rock containing them was yet loose mud or 

 sand. A slab three by eight feet in size, now in the Yale College cabinet 

 (from Greenfield, Mass.), is covered throughout with such impressions; and 

 as the impressions are slightly oblong and oblique, they bear evidence of the 

 direction of the wind at the time of the short brisk shower. The slab is 

 crossed by a line of footprints showing that an animal of long stride 

 (probably a Dinosaur) walked over the mud-flat just before the shower ; 

 for there are rain-prints in the tracks. This is an example of the 

 geoglypJiics from which the geologist derives 

 facts for geological history. Another les- 

 son, too, comes from the rain-prints, for 

 they show that it rained millions of years 

 since. 



(17) Other markings observed at Green- 

 field, Portland, and other places in the Con- 

 necticut valley, are scratches and grooving s 

 made apparently by a floating log, one end 

 or branch of which dragged in the mud. 

 Others found there and elsewhere are the trails of Worms, and tracks of 

 Insects, Crustaceans, Repitiles, and other animals, all of which give instruction 

 in many ways. 



