PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 509 



down its rain as it progressed. It reached us, in our elevated position, in 

 the form of a dense fog, as all clouds appear when we are in their midst. 

 It first struck our mountain at a point about five hundred feet below its 

 smnmit, and then rolled along amidst the trees to the top of the ball. 

 While hovering- there, as a hen over her brood, it sent an arm down the 

 eastern side of the mountain, above the tree-tops, to a distance of several 

 hundred feet; and then, as if reluctant to lose any portion of its mass, this 

 arm was drawn up ag-ain into the bosom of the cloud. Rendered lig-ht and 

 airy, from tlie loss of its rain, the cloud soon swept off to the eastward, so 

 that our measurements could be completed. 



Nearly all the balls in sig^ht, more than a half-dozen in number, and many 

 of the liig'her portions of the lower ranges of these mountains were repeat- 

 edly covered by rain-clouds during the day, which were either formed T7pon 

 them, or floated to them from one or another of the surronnding elevated 

 points. Four or five of these clouds passed up Valley river toward us, but 

 were generally exhausted of their rain before reaching our positions. The 

 valle\' is narrow, being little more than a mile in width, and runs in a 

 southwest direction to the Hiwassee river. 



' These showers presented varied appearances as they succeeded each 

 other. The first was from a cloud, the margins of which were equal in 

 depth and density to the main part of its body. Its breadth was net-.rly 

 equal to the width of the valley. There being little wind, the rain fell 

 vertically, and presented the appearance of a large curtain of semi-trans- 

 parent gauze, suspended from the cloud to the earth, having a length of 

 two thousand feet. A second shower fell, an hour afterward, from a cloud 

 with attenuafed margins but dense centre. Tlie sheet of water whicli fell 

 from it, presented the appearance of a semi-transparent fog in its centre, 

 but it gradually shaded off toward the margins into a misty haze, scarcely 

 obscuring the objects in the back-ground. A third, which occurred during 

 our descent, was from a dense black cloud that overshadowed the valley 

 and half the adjacent mountains. It had also great length to the west- 

 ward. The bod}' of water which it afforded was so dense, and the distance 

 through which the eye had to penetrate so great, that every object in the 

 back-ground was as completely obscured as though the pall of midnight 

 had been drawn across the valley. 



We had reached a position two thousand feet below the summit, and one 

 thousand above the base of the mountain, when this shower had so far 

 passed over as to allow the sun to shine out brilliantly from the clear sky 

 in the west. Immediately a rainbow of the greatest beauty was produced. 

 The top of its arch reached a little above the top of the ball, which we had 

 just measured, thus throwing the main part of the bow below its level, and 

 giving it a back-ground of the richest green Which the foliage of the moun- 

 tain could afford. Two mountains of unequal height intervened between 

 us and the ball. The nearest one was much the lowest, while the other 

 rose half-way to the summit of the ball. Upon the entire slope, the lines 

 of the rainbow were presented in a richness of color far excelling any 

 thing of the kind I had ever witnesssd before ; the accompanying secon- 

 ondary bow being about as brilliant as the ordinary rainbows of the low- 

 lands. 



