Mabch 19, 1909] 



SCIENCE 



473 



density, he will reach the conclusion that the 

 present apparently close agreement between the 

 observed ellipticity and the theoretical ellipticity 

 due to rotation is not a proof of a former liquid 

 state. 



He will conclude that it is merely an indication 

 of the strength of the material in the interior of 

 the earth, and that the evidence is far from being 

 suflScient to prove that the strength of the ma- 

 terial in the interior, available to resist stress- 

 diflferences, is now or ever has been so small as to 

 justify the statement that the material is or has 

 been a liquid. 



Atomic Theories: L. T. Mobe, University of Cin- 

 cinnati. 

 An Electrical Method for Determining the Amount 

 of Moisture in Grain and Other Materials:^ 

 Akthont Zelent, University of Minnesota. 

 Two plates or pointed conductors made of dis- 

 similar metals are inserted into the material in 

 which it is desired to laiow the amount or per- 

 centage of moisture. These plates or points form 

 the electrodes and the moisture the electrolyte of 

 a voltaic battery which causes a current to flow 

 through the galvanometer, whose magnitude de- 

 pends on the amount of the moisture. 



The size of the scale divisions representing any 

 definite amount of moisture is first determined 

 experimentally for each particular kind of ma- 

 terial. When the temperature of the material 

 under test influences the magnitude of the deflec- 

 tion, a proper galvanometer shunt is used with its 

 lugs labeled in degrees, so that, when set to indi- 

 cate the temperature of the material, the proper 

 values for the amount of moisture are obtained 

 regardless of the temperature. 



In the case of corn, it was found desirable to 

 have the two dissimilar metals of copper and zinc 

 in the form of points which are pressed into the 

 germ of the individual Ijernel. The deflection 

 obtained indicates directly the percentage of 

 moisture in the whole kernel. A curve exhibiting 

 the relation between the deflection and the per- 

 centage of moisture was shown. 



This apparatus is found to be capable of giving 

 values accurate to about 0.1 per cent. 



On the Extra Transmission of Electric Waves: 

 P. C. Blake, Ohio State University. 

 With the same apparatus that Blake and Foun- 

 tain (Phys. Rev., XXIIL, p. 257, 1906) used, the 

 conditions insisted upon by Dr. Sehaefer (Phys. 

 Rev., XXIV., p. 421, 1907) were fulfilled. Two 

 "Patent pending. 



diaphragms, 2.5 meters square and of aperture 

 24 by 32 cm., were inserted, one near the vibrator 

 mirror, the other near the receiver mirror with 

 the resonator system between them. Nine per 

 cent, of extra transmission was found, using long 

 strips 3 cm. apart on plate glass. Afterward only 

 a single diaphragm was used, it being placed as 

 near as possible to the receiver mirror. Its aper- 

 ture was 68.5 cm. long and of a width that was 

 varied from 8 to 61 cm. The extra transmission 

 was 15 per cent, in amount and independent of 

 the width of the diaphragm aperture. 



Taking this last value as a true measure of the 

 extra transmission it would appear that the use 

 of diaphragms, especially when their apertures are 

 as small as Sehaefer demands, introduces errors 

 due to diffraction, but in no case does it com- 

 pletely mask the effect of extra transmission. 



Then the vibrator was varied by short steps a 

 distance of 1 cm. either way from its usual focal 

 position of 7.5 cm., a single diaphragm of aper- 

 ture 68.5 by 16 cm. being used near the receiver 

 mirror. No change in the extra transmission was 

 obtained, although these vibrator changes changed 

 the beam from one quite strongly divergent to a 

 convergent beam. 



Entladungsstrahlen : Elizabeth R. Laied, Mount 



Holyoke College. 

 A Spectrometer for Electromagnetic Radiation: 



A. D. Cole, Ohio State University. 



The continuation of work on diffraction of elec- 

 tric waves, on which a partial report was given 

 at the New York meeting of the American Asso- 

 ciation for the Advancement of Science, made ic 

 desirable to have a more convenient means of 

 quickly changing the angle between the direction 

 of wave propagation and the line connecting the 

 diffraction edge or slit with the receiver. This 

 resulted in a mounting for the several parts of the 

 apparatus similar to that of the parts of a work- 

 ing spectrometer for light radiation. 



It seemed worth while to develop the design 

 still farther, so that the apparatus might later 

 be used by advanced students as a more con- 

 venient means of repeating the classical experi- 

 ments of Hertz, Boltzmann and Righi. The use 

 of the conventional spectrometer design serves to 

 strengthen the force of the analogy between elec- 

 trical and light radiation, particularly when used 

 for lecture demonstrations, for which it is well 

 adapted. Drawings of the apparatus with a con- 

 siderable variety of accessories for special uses, 

 were shown and described. By a few simple 



