Eebbuaet 6, 1920] 



SCIENCE 



141 



tures with the same concentrations in soil 

 solutions. 



3. " The toxicity of soluble salts in the soil 

 was found to be in the following order : sodium 

 chlorid, calcium chlorid, potassiiun chlorid, 

 sodium nitrate, magnesium chlorid, potassium 

 nitrate, magnesium nitrate, sodium carbonate, 

 potassiiun carbonate, sodium sulfate, potas- 

 sium sulfate, and magnesium sulfate." 



Since the author did not determine and did 

 not know how much of these salts were 

 actually in the soil solution he could not very 

 well indicate their relative toxicities. It will 

 be noted that sodium carbonate is placed near 

 the bottom of the list as a relatively harmless 

 salt, whereas, as a matter of fact, it is one of 

 the most toxic salts occurring in the alkali 

 soils of the west. 



4. "Land containing more than the follow- 

 ing percentages of soluble salts are probably 

 not suited without reclamation to produce 

 ordinary crops : In loam, chlorids 0.3 per cent. ; 

 nitrates, 0.4 per cent.; carbonates, 0.5 per 

 cent. ; sulfates, above 1.0 per cent. In coarse 

 sands, chlorids, 0.2 per cent.; nitrates, 0.3 per 

 cent; carbonates, 0.3 per cent, and sulfates, 

 0.6 per cent." 



Here again the author draws conclusions 

 without having accurate data on which to base 

 them. If the above percentages were to be 

 adopted by chemists in determining the suit- 

 ability of alkali soils in the field for crop 

 growth, the results would be misleading in the 

 extreme. The results are not in accord with 

 those obtained by determining toxic limits 

 in field studies, nor with laboratory experi- 

 ments in which toxicity is related to the alkali 

 actually in the soil solution instead of to that 

 which was put in. 



In the paper by Harris and Pittman, pub- 

 lished in IsTovember, 1918, the authors have 

 adopted the same erroneous method but they 

 are more careful in drawing conclusions as 

 the absorption of the salts added is apparently 

 recognized but is not determined and related 

 to crop growth. The conclusion, however, 

 that " Loam soils and soils with a high water- 

 holding capacity may be successfully farmed 

 at a higher alkali content than others" may 



possibly be true but there is no data given 

 in the paper which justifies the conclusion, for 

 the per cent, of alkali salts recoverable from 

 the two kinds of soil was not correlated with 

 crop growth. 



It is also suggested that the results ob- 

 tained by Brown and Hitchcock published 

 under the title " The efFects of alkali salts on 

 nitrification" (Soil Science, Vol. IV., No. 3) 

 and by Singh on the "Toxicity of alkali 

 salts" (Soil Science, Vol. IV., No. 6) would 

 have been more valuable had they been corre- 

 lated with the recoverable salts rather than 

 with the salts added to the soils with which 

 they were working. 



F. B. Headley 



Newlands Experiment Farm, 

 Failon, Nevada 



on high-altitude research 

 I AM beginning to appreciate the difficulty 

 of making one's self understood in a state- 

 ment where matters are suggested rather than 

 explained in detail, and where a critical 

 attitude is urged until a result is actually 

 verified by experiment, even when one feels 

 perfectly confident beforehand what the result 

 will be. The present statement is written for 

 the purpose of correcting any misconceptions 

 that may have arisen from my recent presa 

 statement. 



First, the time necessary for a preliminary 

 exploration of the atmosphere will be re- 

 quired chiefly for the preparation. It is not 

 like an exploration of " darkest Africa," for, 

 with the proper rocket apparatus and instru- 

 ments, each flight will occupy but a short 

 time; and not many will be needed to obtain 

 a very considerable amount of information, 

 such as an accurate knowledge of densities, 

 that would be needed for any further devel- 

 opments. 



The expense also will be chiefly that for 

 preparation; namely, for machine construc- 

 tion and tests. A final form of apparatus, 

 designed for reaching any particular altitude, 

 should not be expensive. This is, of course, 

 true of any product that requires machine 

 development. 



