242 



SCIENCE 



[N. S. Vol. XXXVIII. No. 972 



historic earthworks found in this country along 

 the Mississippi and Oneota rivers. These earth- 

 works consist of three types, the most common 

 being the Circular Mound. Followiiig that the 

 Long Embankment, these latter sometimes having 

 a length of upwards of four hundred feet, and 

 where found on the bluff tops they uniformly fol- 

 low the divides separating the gullies and ravines 

 opening into the main river valley. Following 

 these in frequency of occurrence are the Effigy 

 Mounds. It is somewhat difficult to say what 

 particular animal or bird these mounds are in- 

 tended to represent, but there is quite a variety. 

 Near McGregor is a group of three which are in 

 a very fine state of preservation and were un- 

 doubtedly intended to represent the buffalo. 

 Along the Oneota River, but not found on the 

 Mississippi, are embanlonents in the form of a 

 circle. Some of these are on the bluff tops and 

 some on the river bottoms. It is more than likely 

 that a part of them are the remains of camps 

 fortified with palisades, and others may have been 

 built for some ceremonial purpose. The circular 

 mounds are probably mostly burial mounds, and 

 probably of great age, as no skeletal remains are 

 found in any of them, and there is also a great 

 scarcity of flint or other implements or of pottery. 

 An Electrical Method of Measuring Certain Small 

 Distances, and Some Interesting Besults: F. C. 

 Bbown. 

 The Variation of the Resistance of Antimonite 

 Cells with the Current Flowing, and the Prob- 

 able Interpretation of this Variation: F. C. 

 Bkown. 

 The Change of Young's Modulus of a Soft Steel 

 Wire with Electric Current and External Seat- 

 ing : H. L. Dodge. 

 Are the Photo-electric Sigh Potentials Genuine: 



Paul H. Dike and F. B. York. 

 Some Dangers in Statistical Methods: Abthxfr G. 



Smith. 

 The Problem of the Vision of an Illuminated Sur- 

 face: L', P. SlEG. 

 On the Existence of a Minimum Volume Solution: 



LeEot D. Weld. 

 Phase Relations and Sound Beats when the Tones 

 are Presented One to Each Ear : G. W. Stewart. 

 It has long been known that beats produced by 

 two tones, presented one to each ear, are not quite 

 like the beats produced when the same tones are 

 presented to one of the ears. The experimental 

 arrangement in this experiment was such that the 



frequency of beats could be changed, the tones 

 being presented one to each ear, and the difference 

 of phase could be observed optically. The observed 

 results were as follows : When the beats were more 

 frequent than one per second the beats were sim- 

 ilar to ordinary beats except that there was no zero 

 intensity minimum. This fact is not new. When 

 the beats became less frequent than one per second, 

 it was possible to persuade the hearer that there 

 was a secondary maximum in the neighborhood of 

 opposition in phase. When the beats became less 

 frequent than one each five seconds the maximum 

 intensity is difficult to select, the secondary max- 

 imum being more pronounced. Further, the sec- 

 ondary maximum seems to consist of two maxima, 

 one just before and one just after opposition 

 of phase. The tone at equality of phase is differ- 

 ent in quality to that at the secondary maxima, 

 the former being like the tone of the fork and the 

 latter more of a noise. Some observers can not 

 get the effect at all. When one of the tones is 

 received through the teeth with the other received 

 at one of the ears, there appears to be only one 

 maximum, and that at opposition of phase. The 

 proposed explanation involves a combination of a 

 skuU tone and an ear tone; but is too complicated 

 to present in an abstract. The theory agrees with 

 the experiments in a quantitative way if the 

 velocity of soimd in the skull is from two to three 

 times that in air. The presence of a maximum at 

 equality of phase does not seem to permit of ready 

 explanation if the possibility of interference be- 

 yond the cochlea is rejected. The experiments 

 were with forks of frequency 128. The theory 

 should be tested under varying conditions. 



The Use of the Bayleigh Dish in the Determina- 

 tion of Relative Sound Intensities: Habold 

 Stiles. 



During the summer of 1912 some experimental 

 work was done at the State University of Iowa 

 by G. W. Stewart and Harold Stiles partly in- 

 tended to test the Eayleigh disk in the determina- 

 tion of relative sound intensities. The apparatus 

 was mounted on the roof of the new physics 

 building and results obtained experimentally were 

 in close agreement with the theoretical values ob- 

 tained by Stewart" for soxmd intensities in the 

 neighborhood of a rigid sphere, the source of 

 sound being on the sphere. Air currents, the in- 

 constancy of the sound source and more particu- 

 larly the absorption of energy by the Eayleigh 



^Phys. Rev., Vol. XXXVIII., No. 6, December, 

 1911. 



