March 30, 1900.] 



SCmNGE. 



511 



This article attracted considerable attention 

 and was reprinted entire or in part in other 

 journals. 



Among the letters received at the time of 

 publication, the following substantiate the last 

 part of the 5th conclusion, viz, that floating 

 sand is much more common than is ordinarily 

 supposed : 



Professor William Morris Davis wrote, Janu- 

 ary 28, 1896 : '■! have noticed the same thing 

 (floating sand) on the tidal currents of Cape 

 Cod." 



Mr. Henry W. Nichols of Field Columbian 

 Museum, Chicago, wrote, February 3, 1896 ; 



" I would Hive to add another instance. A t Cohas- 

 set, Mass., a town about twenty-five nliles south of 

 Boston, there is a land locked inlet from the sea, 

 known as Little Harbor. There are here and there 

 along its shores, small beaches of angular gravel and 

 sand. When there is no wind, the tide rises gently 

 on these beaches without even a ripple, and gently 

 lifts grains of dry sand which form such patches as 

 you describe a foot or more in diameter. Some days 

 such floating patches are very numerous, and may be 

 seen going out with the tide all the way from the 

 head of the Harbor to the outlet over a mile distant. 

 The rook of the region is granite and the sand is 

 probably derived from it. The grains are very angu- 

 lar. Without thinking much upon the subject, I 

 have always considered that a film of air adhered to 

 the grains and kept them from wetting, and that the 

 floating was due to surface tension as in the case of 

 the familiar experiment with a needle." 



In the American Geologist for November, 

 1898, Professor George E. Ladd discussed the 

 ' Geological Phenomena resulting from the Sur- 

 face Tension of Water.' Under the caption 

 ' Floating Materials' (p. 283) he says : 



" It is not uncommon to see materials of a higher 

 specific gravity than water floating upon its surface. 



" The principle involved is again that of surface 

 tension, and substances thus float only when the at- 

 traction for the water is less than the latter's surface 

 tension. 



" The geological results of this principle are chiefly 

 the floating and shifting from place to place of sands. 

 While I have observed such an occurrence on many 

 occasions, in diSerent places, the most important 

 noticed was in Massachusetts, at the mouth of the 

 Merrimac River. Here the northern end of Plum 

 Island, which is a vast accumulation of sand, shuts in 

 the harbor of Newburyport on the southeastern side. 

 The action of the winds, of the waves, in time of 



storm, and the shifting currents (the position of the 

 harbor's channel varying rapidly) result in the for- 

 mation of numerous bays or 'basins 'in the sandy 

 Island, on the protected side, often occupying exten- 

 sive areas. The largest of these, having a circum- 

 ference of something over a mile, has endured for the 

 past forty or fifty years. The sand consists mainly of 

 coarse, sharply angular quartz, but much feldspar is 

 present, some mica, and numerous fragments of 

 schistose and gneissic rocks. Whenever, on the re- 

 treat of the tide, the beaches and the exposed bars 

 are dried by the sun's beat, the returning water, if 

 not too greatly disturbed by unfavorable winds, lifts, 

 as it creeps up the slope, the whole superficial film 

 of sand, including large thin pebbles of schist, and 

 floats it gently on the surface. The surface of the 

 water, near the shores bearing the sand, commonly 

 moves out towards the main river, even when the 

 tide is rising, the incoming water flowing beneath. 

 " I have estimated that in the course of a year 

 something like a thousand tons of sand, at a mini- 

 mum, are lifted and borne away to new resting 

 places by the floating power of surface tension at this 

 locality alone." 



During the present year Dr. Erland Norden- 

 skiold's communication to Nature (January 18, 

 1900, p. 278) on ' Floating Stones,' seen by 

 him during his recent visit to southwest Pata- 

 gonia, has evidently been read with great in- 

 terest in England and has been the means of 

 calling forth a number of statements concern- 

 ing floating sand and other mineral matter, 

 such as fragments of shells. Neither Dr. 

 Nordenskiold nor the other correspondents seem 

 to have been aware of the papers published on 

 that subject by Messrs. Graham, Ladd and my- 

 self, though printed in journals of wide reputa- 

 tion and extended circulation. Dr. Norden- 

 skiold says ; 



"Whilst rowing in the long and narrow chan- 

 nel of Ultima Esperansa, to study the plankton, we 

 observed, when the sea was calm or only agitated 

 by a slight swell, small fragments of slate which 

 floated upon the surface packed together in larger or 

 smaller clusters. They drove hither and thither in 

 the neighborhood of the shore, until they were driven 

 away by the strong current which at intervals swept 

 forward in the channel. The quantity was consider- 

 able ; for instance, 700 of them were obtained at one 

 cast of the net in a few minutes. The stones had evi- 

 dently drifted out from the beach, which consisted 

 mainly of similiar stone fragments washed off from the 

 cliffs composed of a bituminous mesozoic slate. The 



