APPENDIX 



495 



blende, etc., calcareous particles being either absent or very scanty. 

 The magnetite mostly gathers among the finest materials, being 

 there especially frequent in the sand blown along the ground and in 

 the medanos that have travelled four miles from their starting-place, 

 the proportion making up 25 or 30 per cent, of the total. It is also 

 well represented amongst the finest materials of the sand blown 

 through the air. The grains of magnetite are always smaller than 

 those of the felspar. Thus in the case of the sand blown through 

 the air the magnetite grains average 0*12 mm. in size and the felspar 

 grains as much as 0'23 mm. The beach sand from between the tide- 

 marks has the same composition as the sand of the medanos and of 

 the plains. 



It is interesting to notice how the fine materials are appropriated 

 by the medano as it proceeds inland from the coast. In the beach 

 sand blown up the hill-slopes, but below the place where the first 

 medano shapes itself, there is only 11 per cent, of fine materials. 

 When the medanos have travelled a mile inland the proportion is 

 about 40 per cent., and when they have extended four miles from 

 the starting-place it is 55 per cent. Except when composed of 

 softer calcareous materials, as in the case of the seolian deposits of 

 the Bahamas, " the ordinary drifted sands of seaside dunes show 

 little rounding " (see Grenville Cole's Practical Geology, 1898, p. 189). 

 This is especially true of the dunes or medanos of the Ancon district. 

 The sand-grains of the medanos four miles from the beach were 

 most affected by attrition; but even they could only be described 

 as sub-rounded. The sand-grains of the medanos a mile from the 

 starting-place and the sand blown through the air were still less 

 rounded, and could be only termed sub-angular. The extra-coarse 

 sand of the wavelets or ripplets spread over the surface of the medano 

 plains, however, displayed the effects of attrition in a marked degree, 

 the angles of the grains being well rounded. 



Note 35 (pp. 55, 484). 



Bottle-drift in high latitudes of the North Atlantic. 



The tracks are given in the American charts for several bottles 

 thrown into the sea between Newfoundland and Greenland which 

 were cast up on the coasts of Ireland, Scotland, and Norway, reach- 

 ing even to the North Cape, the velocity of the swiftest being eight 

 to nine miles a day. One, however, dropped over about 100 miles 

 south-east of Cape Race, was recovered on the south coast of Iceland 

 sixty-seven days afterwards, the distance of 1950 miles having been 

 accomplished at a minimum daily rate of twenty-nine miles (see 

 No. 95 in the U.S. Pilot Chart of the North Atlantic for November 

 1908). The most northerly traverse of the North Atlantic that is 

 illustrated in the American bottle-drift charts is one marked 109 in 

 the U.S. chart just named. Here a bottle drifted from a position 

 about 300 miles south-east of Cape Farewell to the North Cape of 

 Norway. However, through a printer's error, the daily rate is given 

 as 34*6 miles instead of 3*46 miles. But bottle-drift from off the 



