316 



SCIENCE 



[N. S. Vol. XLII. Nq. io79 



of the swing of the pendulum; the pin is 

 brought in contact with the plate, closing an 

 electric circuit, which actuates a time-marker 

 writing upon the recording surface. As the 

 lever rebounds, and does not make contact 

 again until it has received another impulse, 

 the electric closure is almost instantaneous. 



The great advantage of this simple arrange- 

 ment is that it does not involve any alteration 

 in the apparatus with which it is used. A 

 cork disc or ball slipped upon the end of the 

 vibrating rod is the only addition to the met- 

 ronome that is required. The disadvantages 

 of a mercurial contact are avoided, which is 

 always desirable, unless special reasons re- 

 quire it. 



The apparatus has been tested with a record- 

 ing tuning fork and it has been found to give 

 satisfactory results with the metronome, 

 which, of course, should only be used in ex- 

 periments of moderate accuracy. The key is 

 probably much more reliable than the metro- 

 nome with which it is used. Comparative 

 tests of the key and the well-known tambour 

 device for recording the beats of a metronome 

 were also made, and the key was found much 

 more convenient and accurate. 



I have ventured to describe this inexpensive 

 piece of apparatus, as its simplicity and effi- 

 ciency would seem to commend it to all those 

 who employ the metronome in recording time. 



Frederick W. Ellis 



MoNsoN, Mass. 



SOCIETY OF AMERICAN BACTERIOLOGISTS 

 V 

 Industrial Bacteriology 

 Under the supervision of E. E. Buchanan 

 Frohlems in Soil Bacteriology : Jacob G. Lipman. 

 The student of soil bacteria, and of other soil 

 microorganisms, is often struck by the fact that 

 there is, apparently, localization of one or another 

 of the species in certain spots. To what extent is 

 this localization characteristic of fields, small areas 

 in any one field, or soil particles of different min- 

 eralogical or other origin? We know, of course, 

 that the water films surrounding the individual soil 

 particles represent solutions of varying composi- 

 tion and concentration. But we have no knowl- 



edge, except of an indirect character, as to the 

 very interesting differences which must exist as 

 to the numbers and kinds of bacteria in the water 

 film surrounding individual particles. 



From other fields of bacteriology, we know that 

 there may be associative action, and likewise an- 

 tagonism, among species of soil bacteria. But we 

 know practically nothing of these relations in the 

 soil, nor how these relations may be modified by 

 soil treatment or by climatic conditions. 



It has always been my belief that the beneficial 

 results ascribed to applications of commercial fer- 

 tilizers or of other materials may be due as much 

 to the action of such materials on soil microorgan- 

 isms as to the action on the crops themselves. 

 There is need now for the study of soil bacterio- 

 logical problems from this point of view. 



Another problem which is widely recognized of 

 importance to soil fertility is the formation of so- 

 called humus in the soil. Admitting that humus is 

 the result of biological activities, it is for us to 

 discover how the composition of the resulting prod- 

 uct is affected, not only by vegetable and animal 

 substances from which it is derived, but by the 

 type of microorganisms concerned in its formation. 



To the problems already mentioned, I might add 

 the systematic study of temperature, moisture, aera- 

 tion and pressure as factors in influencing bacterio- 

 logical activities in the soil. It is possible also, 

 that so-called stimulants, like manganese, copper, 

 zinc, etc., may react on the activities of soil micro- 

 organisms. These problems should receive the at- 

 tention of, preferably, a large number of workers. 

 It may be added that these and other problems 

 studied systematically will help to throw light on 

 the production and modification of plant food in 

 the soil and on the great industry of crop produc- 

 tion. 



The Solution Versus the Soil Method for the Bac- 

 teriological Examination of Soils: P. E. Brown. 

 Prom a careful study of the methods which have 

 been employed for the bacteriological examination 

 of soils, it is concluded that the "fresh soil" 

 method is the most rational which has yet been de- 

 vised. A recently proposed modification of the 

 solution method, while eliminating some of the ob- 

 jections to the old method, is considered to possess 

 many objectionable features, so many as to be of 

 very questionable value for the interpreting of re- 

 sults from the fertility standpoint. It is urged 

 that careful comparative tests be carried out, in 

 order to settle definitely the question of which is 

 the "best" method for the bacteriological exami- 

 nation of soils. 



