April 5, 1907] 



SCIENCE 



525 



There is a great difference among con- 

 densers as to power factor and temperature 

 coefficient, and a condenser should never be 

 purchased without a knowledge of these 

 constants as well as a knowledge of its 

 capacity. 



The Diffraction of Electric Waves of Short 



Wave-length: A. D. Col.e, Ohio State 



University. 



Peculiarities observed in a quantitative 

 study of the reflection of electric waves 

 seemed to be due to diffraction and led to 

 this study. These peculiarities were: (1) 

 A sudden increase in the amount of energy 

 passing through a slit of increasing width 

 when it becomes more than a quarter wave 

 wide, (2) the amount of energy reflected 

 from a narrow mirror was found to be 

 greater than that passing through a slit of 

 the same width provided each is but a 

 small fraction of a wave-length wide, (3) 

 irregularities noticed when screeng were in- 

 troduced to cut off direct radiation. 



The earlier investigations of Trouton, 

 Zehnder and Righi were carried out with 

 apparatus which did not give quantitative 

 results. A modified form of Klemencic 

 thermo-receiver made it possible to study 

 the distribution of refracted energy quan- 

 titatively. A Righi exciter, actuated by 

 an induction coil and Wehnelt interrupter, 

 was used for generating the waves. 



The lateral distribution was studied and 

 the result exhibited by curves for the fol- 

 lowing cases : (1) A slit about three fourths 

 of a wave-length wide showed a broad 

 spreading of energy, with a central 'bright 

 band' having a dark band and weaker 

 bright band at each side. Their locations 

 agreed with the optical formula, A,=a sin 0. 

 (2) A wider slit showed interference bands 

 nearer together. (3) Case of energy dis- 

 tribution behind a thin metallic edge placed 

 on the axis of a plane wave front. (4) 

 Similar with the edge displaced laterally. 



Trouton 's discovery that the system of 

 nodes and loops formed by reflection at 

 perpendicular incidence from a small plane 

 mirror is shifted outward if the mirror is 

 made with dimensions of a wave-length or 

 less was verified and the amount of the 

 shifting measured for several cases. 



The study of diffraction is being con- 

 tinued. 



Final Report on Ether-drift Experiments: 

 Edwakd W. Moelet and Datton C. 



MiLLEE. 



At the Philadelphia meeting an account 

 was given of experiments to detect ether 

 drift. These observations gave no indica- 

 tions of a drift of the ether. It has been 

 suggested that the negative results are due 

 to the influence of the heavy stone walls of 

 the building within which the apparatus 

 was mounted. The interferometer has, 

 therefore, been mounted on high ground 

 near Cleveland, and covered in such a man- 

 ner that there is nothing but glass in the 

 direction of the expected drift. It was 

 much more difficult to make observations 

 in this location than in the building ; satis- 

 factory observations could only be made on 

 a cloudy evening following a cloudy day, 

 when the temperature changed very slowly. 

 The temperature effects could never be en- 

 tirely eliminated. The conclusion from 

 many observations is that there was no in- 

 dication of a drift of the ether through the 

 interferometer. The expected drift would 

 produce a displacement of the interference 

 fringes of 1.53 wave-lengths; the above 

 result is probably certain to one eightieth 

 part of the whole. 



The Optical Analogue of Certain Electrical 



Experiments: William B. Caktmel, 



Harvard University. 



The recent experiments of Messrs. Blake 



and Fountain show that the amount of 



electric radiation transmitted by sheets of 



glass, may be increased by covering the 



