JuLI 7, 1922] 



SCIENCE 



21 



very clearly are not indigenous to the flood 

 plain materials that form the ridge. The sup- 

 position is that they were forced up from below 

 by gaseous and water pressure that gave rise 

 to the craterlets. 



Age : No evidences as to age was obtained 

 by the writer. However, as similar craters are 

 found farther to the north and are there shown 

 to have been formed at the time of the New 

 Madrid earthquake, it is logical to assume that 

 these were formed during the same disturb- 

 ances. 



E. T. Thomas 



Univeesitt op Arkansas 



AZOTOBACTER IN SOILSi 



Some time ago the writer^ called attention to 

 the apparent relation existing between the 

 presence of Azotobacter in soils and the abso- 

 lute reaction of the soil. At that time less 

 than one hundred soils, all local, had been 

 examined and the reaction was determined 

 eolorimetrieally upon an extract of the soil. 

 Since then 418 samples of soil collected from 

 39 counties in Kansas and 25 states other than 

 Kansas have been cultured for Azotobacter and 

 their presence or absence in such cultures com- 

 pared with the absolute reaction of the soil 

 determined eolorimetrieally upon an extract of 

 the soil, and also with the reaction of the soil 

 determined eleetrometrically upon a suspension 

 of the soil. 



These soils have iDeen arbitrarily divided 

 into two groups : those, the hydrogen-ion con- 

 centration of which was found to be greater 

 than 1 X 10—°; and those with a lower hydro- 

 gen-ion concentration. This particular division 

 point has been chosen because the large amount 

 of data that have been accumulated indicate 

 that the maximum hydrogen-ion concentration 

 tolerated by Azotobacter is very near this point. 

 Comparing the presence and absence of Azoto- 

 bacter in these two soil groups with the reac- 

 tion we can, by making use of Yule's^ associa- 



1 Contribution No. 47, Department of Bacteri- 

 ology, Kansas Agricultural Experiment Station. 



2 P. L. Gainev: Science, N. S., 48, pp. 139- 

 140; Jour. Ag. Ses., 14, pp. 265-271. 



3 G. Udny Yule, Phil. Trans. Boy. Soc, Ser. A, 

 Vol. 194, pp. 257-319. 



tion correlation formula, obtain a mathematical 

 expression for the association or correlation 

 existing between the reaction and the presence 

 or absence of Azotobacter. 



An application of this formula to our data 

 gives, when the reaction of the soil was deter- 

 mined eolorimetrieally, a coeificient of 0.956. 

 When the reaction was determined eleetromet- 

 rically the coefflcient was found to be 0.942. 



It has been demonstrated in this laboratory 

 that when Azotobacter are introduced into a 

 soil with a hydrogen-ion concentration gi-eater 

 than 1 X 10— ", and not containing Azotobacter, 

 they can exist therein for an appreciable length 

 of time. Considering the relative ease with 

 which soils may become inoculated under nat- 

 ural conditions, and also the probability that 

 other conditions may inhibit the growth of 

 Azotobacter in soils the reaction of which is 

 favorable, it is believed that an association, or 

 correlation eoefScient as high as that indicated 

 above is significant in indicating the influence 

 of the hydrogen-ion concentration of a soil 

 upon the ability of that soil to support Azoto- 

 bacter. 



P. L. Gainet 

 Kansas AoEicrrLTURAL 

 Experiment Station 



GENERAL MEETING OF THE AMER- 

 ICAN CHEMICAL SOCIETY 



The sixty-third general meeting of the Amer- 

 ican Chemical Society was held at Birmingham, 

 Alabama, Monday, April 3, to Friday, April 7, 

 1922, inclusive. The council meeting was held 

 on the third, the general meeting on the morn- 

 ing and afternoon of the fourth and divisional 

 meetings all day Wednesday and Thursday. 

 Excursions were enjoyed in Birmingham on 

 Friday, and some fifty of the members took h 

 special excursion to Muscle Shoals on Satui'- 

 day. Full details of the meeting and progi-am 

 will be found in the May, 1922, issue of the 

 Journal of Industrial and Engineering Chem- 

 istry. The registration was 381, coming from 

 36 states and one from the island of Mauritius. 

 Twenty-eight ladies attended the meeting. 



General public addresses were given by 

 Carlile P. Winslow, director, U. S. Forest 

 Products Laboratory, on "The development of 



