182 Dr Fleming on a Simple Form of Rain-Gauge. 



trees, no rock is visible in the water-course, except a vein of 

 trap at a mill ; the distance from bank to bank varies from a 

 furlong to a quarter of a mile, and the clay is so hard and 

 tenacious that it rises at several points almost vertically, like 

 a wall, from the water edge to the height of more than 100 

 feet. Where the clay was laid open by lateral rivulets, I 

 found grooved stones embedded in it, some of them of chlorite 

 slate. Farther south, sandstone is seen on both sides. The 

 ravine seems, in short, to be an ancient water-course re- 

 opened. The absence of visible rock on the west side, be- 

 hind the clay, may, indeed, suggest the idea that there is 

 nothing but clay in that direction ; but the height and form 

 of the land there, and other circumstances, satisfy me that 

 this is not the case. Perhaps some of the ancient channels, 

 when filled up with the boulder clay, were in the condition 

 described by Playfair. namely, chains of lakes connected 

 by streams whose channels abounded in cataracts. If the 

 idea here thrown out be correct, that some of our rivers are 

 now flowing in ancient channels reopened, it follows that 

 the subsidence and re-elevation of the land through a space 

 of more than 1000 feet, had done very little to disturb the 

 levels. But the subject yet requires investigation. 



On a Simple Form of Rain-Gauge. By the Rev. JOHN 

 Fleming, D.D., &c.. Professor of Natural Science, New 

 College, Edinburgh. Communicated by the Author.* 



The defects with which rain-gauges may be charged, at 

 present, seem referable to inattention to the influence of the 

 wind on the fiilling rain-drop. If the drop was influenced 

 only by gravity in its descent to the earth, the form and posi- 

 tion of the I'ain-gauge would be comparatively of little im- 

 portance. But in addition to its centripetal tendency, regu- 

 lated in velocity by its size and the height of the fall, the 

 rain-drop is frequently acted upon by the wind, and deflected 

 more or less from its normal path, according to the velocity 

 and direction of the cun-ent. While the wind thus influences 



* Read before the Royal Society of Kdiiiburgh, 16th April 18-19. 



