Contributions in geographical exploration . .as described by Davis and Bryan in the above mentionedbulletin, and the calculations for the salt content from theBridge readings were based on their factor as the ratio ^Davis. R. O. E. and Brvan. H. The EKctrical for the Determinationof Soluble Salts in Soils. U. S. I.)cpt. of .-Vgriculture, Bureau of Soils, Bull. 61 1910. 228 The Ohio Journal of Science [Vol. XIX, No. 4, of soil resistance to solution resistance. The use of this factorwas made necessary since the table of resistances and saltcontent did not cover the whole range desi
Contributions in geographical exploration . .as described by Davis and Bryan in the above mentionedbulletin, and the calculations for the salt content from theBridge readings were based on their factor as the ratio ^Davis. R. O. E. and Brvan. H. The EKctrical for the Determinationof Soluble Salts in Soils. U. S. I.)cpt. of .-Vgriculture, Bureau of Soils, Bull. 61 1910. 228 The Ohio Journal of Science [Vol. XIX, No. 4, of soil resistance to solution resistance. The use of this factorwas made necessary since the table of resistances and saltcontent did not cover the whole range desired. A series ofresistances for sodium chloride solution, ranging from to 2500 grams per 100,000 of water was determined onthe Bridge, and by using the factor and interpolating, theresults given in Table II were obtained. No great degree ofaccuracy is claimed for the results, but the measurements areroughly approximate, and give some idea of the soluble salt con-tent in the volcanic ash deposits. Included in the table are two. Photograph by R. F. GriggsDEPOSIT OF BARE ASH ON PILLAR MOUNTAIN, of ferrous iron, acidity, soluble salt content, ammonia, nitriteand total nitrogen content of this ash were made. measurements made with the same instrument on arable soil,the samples being representative of the first six inches. TheKatmai River wash, where finely divided, contains a muchhigher salt content than the normal soil orthe coarse deposits,such as those of the Martin Creek flat. The ash from the w4ndblown drift on Pillar Mountain contains very little soluble saltcontent, a factor possibly entering into the non-fertility ofthis deposit. The two samples from the Katmai Mud Flow showvery little variation, although a twelvemonth elapsed betweenthe collections. The very fine upper layer of ash, as collected Feb., 191W] Salt, Iron, and Acidity oj the Ash 229 from the slopes of Katmai, shows a relatively hi^h water solublecontent, parts per 1()(),
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