250 'Scientific Intelligence. 



9. Measures of Radiation in relation to Resonators in the 

 Region of Short Electric Waves. — It has been noticed by F. 

 Kirchener that the optical properties of Lippeman's emulsion are 

 changed when the emulsion is moistened ; and he explains this 

 by the supposition that the swimming silver particles act as elec- 

 trical resonators and that their time of vibration is changed by 

 the increase of distance apart. M. Paetzold has studied the 

 effect of gratings interposed between the electrical exciter and 

 receiver of short electrical waves, guided by the analogy con- 

 ceived by Kirchener. The gratings were placed at various dis- 

 tances from the receiver and at different angles. When a strait 

 rod exciter was used to produce the waves, a wave component was 

 discovered in a plane perpendicular to the exciter which differed 

 90° in phase from the ordinary component. The effect of a 

 grating in certain positions is to produce often a combined effect 

 of received and emitted radiations. — Ann. der Physik, No. 1, 

 1906, pp. 116-137. J. T. 



10. Electrical Rectifier. — In previous papers A. Wehnelt has 

 described a rectifier for alternating currents which serves the pur- 

 pose of the Cooper Hewitt mercury rectifier, or the Gratz alu- 

 minium rectifier. The cathode is covered with certain oxides 

 which greatly diminish the cathode fall of potential. Such an 

 electrode he terms oxide electrode. When this oxide electrode is 

 property heated and made the cathode, the difference of poten- 

 tial can be made only 18*20 volts, while if the neighboring cold 

 anode is made the cathode, the potential rises to many thousand 

 volts. The electrical current, therefore, will pass readily in one 

 direction and with great difficulty in the opposite direction. 

 Wehnelt ascribes the performance of the rectifier to an increase 

 of ionization at the oxide electrode. — Ann. der Rhysik, No. 1, 

 1906, pp. 138-156. J. T. 



II. Geology and Mineralogy. 



1. United States Geological Survey. Twenty -sixth Annual Re- 

 port, 1901^-1905, of the Director, Charles D. Walcott. 322 pp., 

 26 maps. — The volume contains besides the executive^and financial 

 statements brief reports from the chiefs of parties upon the 

 scientific results of the year's work. The three great branches 

 of work carried on by the Surrey are the geologic, topographic 

 and hydrographic. Connected with the latter is the Reclamation 

 Service, by means of which considerable tracts of arid land will 

 ultimately be brought under cultivation. 



It is of interest to note the amount of the appropriations to 

 the several divisions, as these are in some measui*e indicative of 

 the lines along which the work of the Survey is being at present 

 chiefly pushed. The entire appropriation aggregated 11,484,820, 

 of which 309,200 was assigned for topographic work, 188,700 for 

 geologic work, 14,000 for paleontologic work, 23,000 for chemical 

 work, 200,000 for gauging streams, 50,000 for preparation of report 



