82 Scientific Intelligence. 



the anode side. After twenty hours exposure with a cathode fall 

 of 2800 volts, he obtained a marked Doppler effect corresponding 

 to the positive rays approaching the cathode. This minimum 

 velocity is not constant for different wave lengths, but is approx- 

 imately inversely proportional to the square root of the wave 

 length. — Phil. Mag., Dec. 1909, pp. 895-900. j. t. 



8. Magnetic Potation of Plane of Polarisation in the Ultra- 

 red. — Many investigations have been undertaken to put Fara- 

 day's experiment on a sound theoretical basis. Yoigt has placed all 

 such investigations in two classes, and the author of this paper, 

 Ulfilas Meyer, discusses Drucle's theories, which are largely based 

 upon the electron theory. He finds that with crystals of fluorspar, 

 sylvin and rock salt, the amount of the turning of the plane of 

 polarization diminishes with increasing wavelength. At 8*85 fx it 

 is less than a minute for a thickness of the crystal of l cm and a field 

 strength of 10,000 Gauss units. The influence of ions on this turn- 

 ing is very small in comparison to that of the ions. This con- 

 clusion is reached from the ground of Drude's view of the elec- 

 tron theory, according to which ultra-red absorbtion arises from 

 vibrating ions, while ultra-violet is excited by resonance of 

 rotating electrons. — Ann. der Physik, No. 132, 1909, pp. 607-630. 



J. T. 



9. Instantaneous X-ray photography. — Friedeich Dessauee 

 states the desirability of shortening the time of exposure to 

 X-rays, and describes a powerful apparatus which he has devised 

 for this purpose. It consists of a very large induction coil, fed by 

 a powerful current which on arising to a proper value is quickly 

 broken by a peculiarly constructed fuse. This fuse is a calibrated 

 piece of wire which is surrounded by a moist covering consisting 

 of a mixture of earths. When the wire heats, the water vapor 

 is formed quickly under pressure and the fuse explodes with 

 violence, breaking the current. The author recommends his 

 method to physicians and has obtained Rontgen cinematographs 

 of the movement of the heart. — Physikalische Zeitschrift, Nov. 

 10, 1909, pp. 859-860. J. T. 



10. Light and Sound ; by Wm. S. Franklin and Barry 

 Macnutt. Pp. viii, 344. New York, 1909 (The Macmillan 

 Co.). — This volume is a part of a series of elementary texts ; 

 practically a revision of Nichols and Franklin's Elements of 

 Physics, which it is doubtless designed to replace. The pres- 

 ent ' volume is the third of the new set : Mechanics having 

 appeared in 1907, Electricity and Magnetism in 1908 and Heat 

 being in course of preparation. Improvement is noted in the 

 relegation to an appendix of the 'more detailed discussion of lens 

 systems, of radiation and the addition of 86 problems as exercises 

 on the several chapters. An excellent discussion of wave motion 

 in general is illustrated by particular waves in water. A total of 

 143 pages have been added. Much of the additional matter 

 pertains to practical applications, on the importance of which to 

 elementary students the authors express their opinion in the 



