Februaey 26, 1904.] 



SCIENCE. 



347 



acid was accomplisiied very rapidly. By 

 changing the ratio of water to soil from two 

 to ten. Dyer found from seven to eighteen 

 parts of phosphoric acid per million of dry 

 soil. In Bulletin No. 22 the average for 

 147 analyses of a number of types of soil is 

 7.64 P0„ equivalent to 5.73 P,0„, and for 

 the Eothamsted soils from 10.5 to 19.6 PO^ 

 equivalent to 7.9 to 11.7 P^Oj, figures entirely 

 comparable with those obtained by Dyer. This 

 question of the solubility of the phosphoric 

 acid of the soil in water has been frequently 

 discussed in the literature since the work of 

 KJnop, who used an unreliable method of 

 analysis, and the very interesting replies of 

 Schulze,* Heidenf and others. This early 

 work has been described at length by Johnson:j: 

 and is supposed to be familiar to every tjrro 

 in agricultural chemistry. 



The preceding figures obtained by several 

 investigators using varying proportions of 

 water and soil, digesting for widely varying 

 lengths of time, from a few minutes to many 

 days, using generally gravimetric methods of 



* Landioirthsch. Versueh-Stat., 6, 409, 1864. 

 f Annal. der Landwirthsch., J/S, 189, 1865. 

 t ' How Orops Feed,' pp. 309 et seq., 1890. 



recognized value, will show that the results 

 presented in Bulletin No. 22 are in no way 

 unusual, and that ' merest trace ' is without 

 significance until more specifically defined. 



Several investigators besides Knop have re- 

 ported only traces or no phosphoric acid in 

 water extracts of soils, but generally because 

 of the analytical difficulties in determining it 

 rather than as statements of the actual 

 amounts present. 



The further reference in the ' Added Note ' 

 to Warrington's examination of drainage 

 waters is irrelevant, since it has been perfectly 

 well known since the time of Liebig that drain- 

 ing or leaching a soil does not remove the salts 

 which may actually be in solution in the soil. 

 Agricultural chemists are perfectly familiar 

 with this fact through the classic papers of 

 Liebig, Way and van Bemmelin, as well as 

 others. Moreover, there are quite a large 

 number of figures for drainage and lysimeter 

 waters recorded in the literature which are 

 much larger than that of Warrington, many 

 of them being quoted by Johnson.* 



Hilgard presented an address at the meeting 

 in Washington, attacking Bulletin No. 22, 

 and he also has anticipated publication of the 

 proceedings.! Serious consideration can not 

 be given to this paper, however, since the au- 

 thor claims a non-sequitur to the arguments 

 of Bulletin 22, on general principles rather 

 than specific instances. He devotes almost his 

 entire efEort to a personal attack on the pres- 

 ent Chief of the Bureau of Soils, but in- 

 cidentally expresses his displeasure with agri- 

 cultural chemists of the country because they 

 use the ' official method ' of analyzing soils 

 rather than the one which he proposed a num- 

 ber of years ago. 



Frank K. Cameron. 



Washington, D. C. 



woodcock surgery. 

 In its desire to do nothing by halves, the 

 American public is at present evincing an ex- 

 traordinary fondness for ' nature books.' This 

 would certainly be most commendable, were 



* Loc. cit. 



tThis journal, Vol. XVIII., p. 755, 1903, and 

 Los Angeles Herald, Sunday, December 27, 1903. 



