102 



SCIENCE 



[Vol. LV, No. 1413 



ing with the chemical phases of plant and ani- 

 mal physiologjr indicates general interest in 

 the similarities between chlorophyll and haemo- 

 globin. It would seem that the identity of 

 lipochromes and carotinoids is worthy of equal 

 attention. 



The investigation of what the carotinoids of 

 plants and lipochromes of animals have in com- 

 mon physiologically would seem to be a hope- 

 ful line of work. The fact that they may 

 readily take up oxygen seems to furnish a 

 starting point for thought and work, which 

 will be important, whether the results prove 

 positive or negative. 



Geo. B. Rigg 

 Universitt of Washington 



RATE AND MODE OF SOIL DEPOSITION IN 

 THE PALOUSE AREA OF WASHING- 

 TON AND IDAHO 



During the last eight j'ears the writer has 

 had the opportunity to observe the formation 

 of soils on the Columbia Plateau by the wind. 

 The soils are often a hundred feet deep or 

 more, and are virtually great dunes of silt 

 brought sometimes for great distances. The 

 area where these dunes lie is locally called the 

 "Palouse," well known for its deep and very 

 fertile soils. 



Dust storms are frequent, and, curiously, the 

 dust deposited is generally not raised near the 

 place of deposition. It comes from an area 

 of widely different characteristics. This ac- 

 cords strictly with Richtofen's theory of loess. 

 The loess is formed when the wind moves par- 

 ticles of silt from an arid or semiarid area and 

 deposits them in a more humid one. Once de- 

 posited upon the moister land, the silt particles 

 are not raised again but become a permanent 

 acquisition to the more humid area. Two fac- 

 tors cause the permanency of the deposit, first 

 the moisture in the soil causes coherence in the 

 deposited mass, and secondly the heavier vege- 

 tation forms an entangling mesh. Shaler noted 

 the same conditions prevailing in the formation 

 of loess on the upper course of the Missouri 

 River in Montana. 



In the Palouse great dust clouds flying high 

 in the air often nearly obscure the sun at a 

 time when the soils for many miles around are 



too damp to be blown. A rain or snow fall 

 then clears the atmosphere, carrying the dust 

 particles to earth, and they do not rise again. 

 At the present time drifting seldom takes place 

 but in the past it must have done so. Other- 

 wise the dune shaped hills extending at right 

 angles to the direction of the prevailing winds 

 can not be explained. Thus the deep soUs 

 over the lava plains between the Columbia 

 Valley and the Bitter Root Mountains have 

 been formed at the expense of the drier eastern 

 slope of the Cascade Mountains and the 

 Columbia Valley. 



To measure accurately the amount of soil 

 brought into an area annually is weU nigh 

 impossible. Only under particular conditions 

 is it possible to measure that brought in by a 

 single storm. To do so it is necessary that the 

 soils upon which the deposit takes place be not 

 moved by the wind bringing in the dust. Once 

 deposited, the material must not be lifted again 

 by the same wind, and that brought to earth 

 must be kept separate from older deposits. 



A particularly favorable situation for mak- 

 ing measurement was presented over the east- 

 ern part of the Palouse on January 29, 1917, 

 and at that time a series of collections was 

 begun at Moscow, Idaho, by the writer. From 

 that date to March 23 four dust falls took 

 place, upon all of which measurements were 

 possible. On the afternoon of January 28 a 

 fall of pure white snow took place. The fol- 

 lowing morning it was covered with a coat of 

 chocolate brown dust of variable thickness. At 

 the time practically the whole area was covered 

 with snow. The dust therefore must have been 

 carried nearly a hundred miles and probably 

 was carried twice that distance. 



Measurement of the amount of material de- 

 posited was made by collecting the dust co'sered 

 snow from five diiferent areas of average con- 

 tour, each of four square feet in area. The 

 snow was melted, the water evaporated and 

 the dust weighed. From the result the deposit 

 upon an acre was calcvdated as- 140 pounds. 

 Similar dust falls occurring on March 21, 22, 23 

 brought, respectively, 196 pounds, 184 pounds 

 and 585 pounds per acre as measured in the 

 same way. The total for the four dust falls 

 is 1,105 pounds in 55 days or approximately 



