546 



SCIENCE 



[N. S. Vol. LI. No. 1326 



Hope, at the foot of the Beardmore, Glacier, 

 in 83° 30' S. These field parties in 160 days 

 traveled 1,561 miles, of which distance 830 

 miles were made in laying down from Himt 

 Point the depot at Mt. Hope. Scurvy at- 

 tacked the main party in the field and one 

 man, Spencer Smith, died the day before their 

 return journey was completed. Later Cap- 

 tain Mackintosh and Hayward perished in a 

 blizzard during a short journey — probably 

 from disruption of the ice-pack. Shackleton 

 went at once to the rescue of this party, sail- 

 ing in the Aurora, which was commanded by 

 the veteran polar captain, Davis, in December, 

 1916. The voyage was short and the marooned 

 men were brought safely to Hobart. 



The illustrations are of unusual value, 

 conveying as they do a clearer and more 

 accurate view of polar scenes and lands, and 

 especially as to Caird Coast and Elephant 

 Island. The set illustrating various types of 

 ice are important, and should become 

 standard. 



The narrative is marked by its appreciation 

 of the members of the two expeditions, and 

 from it one is confirmed in the realization 

 that Shackleton is a leader of men of unusual 

 ability and force. Considerate of his subor- 

 dinates, he never spared himself, and under a 

 less able leader the Weddell Sea party would 

 have perished. 



A. "W. Geeely 



SPECIAL ARTICLES 



THE ASH OF DUNE PLANTS 



Sand, the final residue after weather and 

 water have worked their will on the silicate 

 rocks, is possibly the poorest substratum in a 

 chemical sense for the growth of plants. 

 Under the action of glaciers and rimning 

 water followed or accompanied by the hydro- 

 lyzing action of water in the presence of 

 carbon dioxide and lastly subjected to the 

 monotonous attrition of particle against par- 

 ticle acutated by wave motion, nothing is left 

 of the original rock masses except partially 

 rounded particles of quartz accompanied by 

 grains of the more resistant silicate minerals 



and magnetic oxide of iron (FCgO^). The 

 finely divided silt and clay produced during 

 the formation of the sand by wave abrasion 

 and containing the most valuable mineral 

 constituents for plant growth, consisting as 

 they do of particles approaching colloidal 

 dimensions, remain easily in suspension and 

 are carried away by very slight water cur- 

 rents to be deposited far apart from the sand 

 in quiet places. That which remains with 

 the sand after deposition on beach or shore is 

 carried away by the wind and redeposited at 

 a distance, so that beach, shore or dune sand 

 contains a minimal quantity of clay — ^not 

 enough in a handful to cloud a tumbler of 

 water. 



In ordinary sand the silica content varies 

 from approximately 92 to 98 per cent. A 

 part of this exists free as quartz and a part 

 in combination in silicate minerals which 

 have resisted decomposition. The following 

 analyses from Clarke'^ show the composition 

 of sands from various sources. 



A, B. Grlacial sands. 



C. Average of five river sands. 



D. Sea sand. 



E. Sea sand derived from subsilicic ignsouj 



rocks. 



F. Blown sand. 



In spite of its chemical poverty and its 

 inadequacy as a soil for the support of nearly 

 all agricultural plants, sand, nevertheless, has 

 certain physical advantages which are of im- 

 portance and valuable to such vegetation as 



1 ' ' The Data of Geochemistry, " by F. W. Clarke, 

 Bull. 616, U. S. Geological Survey. 



