246 Scientific Intelligence. 



elusion that variation in thickness of layer and variation in pres- 

 sure have similar effect upon absorption is not justified. Changes 

 of volume amount of C0 2 have no influence on the earth's tem- 

 perature so long as the diminution of carbonic acid remains 

 under 80 per cent of the former quantity. — Ann. der Phys., No. 

 1, 1905, pp. 93-105. j. t. 



12. Electromagnetic Waves in the Visible Spectrum. — Many 

 attempts have been made to identify these waves with light 

 waves. Ferdinand Braun forms suitable resonators or " Git- 

 ters" by deflagrating very fine wires stretched on glass plates ; 

 and then observing changes of polarization by means of suitable 

 optical devices directed upon the particles of finely divided 

 metal. According to the electromagnetic theory these " Gitters" 

 should allow little light through if the arrangements of the parti- 

 cles are parallel to the electric vector, and much if they are per- 

 pendicular to it. The author believes that his photographs show 

 a complete analogy between Hertz waves and optical waves. He 

 shows also that the method he employed is of importance in min- 

 eralogical work. — Ann. der Phys., No. 1, 1905, pp. 1-19. j. t. 



13. Damping Galvanometer Deflections. — W. Einthoven con- 

 tinuing his investigations on his new galvanometer, which consists 

 of a silvered quartz fiber stretched in a strong magnetic field, 

 finds that a condenser attached to the terminals of the fiber is of 

 great use in bringing the oscillations to rest even when they are 

 extremely rapid. It is believed that the method will be of great 

 advantage in acoustical investigations and also in physiological 

 work. — Ann. der Phys., No. 1, 1905, pp. 20-31. j. t. 



14. Possible variation in Solar Radiation. — The report of 

 S. P. Langley, Secretary of the Smithsonian Institution, for the 

 year ending June 30, 1904 (noticed on p. 260), contains in the 

 statement of the work accomplished at the Astrophysical 

 Observatory, under the charge of C. G. Abbot, a further discus- 

 sion of the possible variability of the sun first rated in the report 

 of the year preceding. We quote the following paragraphs : 



"Notable progress has been made with the researches you 

 have initiated on the amount of solar radiation and its absorption 

 in the solar envelope and in our atmosphere. Within the last 

 seventeen months three independent kinds of evidence have been 

 collected here, pointing toward the conclusion that the radiation 

 supplied by the sun may perhaps fluctuate within intervals of a 

 few months through ranges of nearly or quite 10 per cent, and 

 that these fluctuations of solar radiation may cause changes of 

 temperature of several degrees centigrade nearly simultaneously 

 over the great continental areas of the world. Further evidence 

 must, however, be awaited to verify this important conclusion. 



The three kinds of evidence referred to are as follows: First, 

 on all favorable days the ' solar constant ' of radiation outside our 

 atmosphere has been determined here, and changes of about 10 

 per cent in the values obtained have been found which cannot be 

 attributed to known causes. Second, the solar image formed by 



