86 Scientific Intelligence. 



wave-lengths 2653*1 and 2644-9 were discovered which belonged 

 to the first main series. Deslandres' nitrogen group which lies 

 between wave-lengths 3009*6 and 2205*3 was investigated, and 

 Deslandres' results confirmed. Seventy new lines of the line- 

 spectrum of nitrogen were also measured. A number of new lines 

 of oxygen were also discovered. — Diss. Halle, 1904. Beiblatter y 

 Ann. der Phys., No. 22, 1904. j. t. 



11. Pressure of Light. — In a sealed communication to the R. 

 Accad. deiLinceiin 1882, opened at the meeting of February 1, 1903, 

 A. Baktoli relates that certain experiments conducted in the year 

 1876 appeared to show that the pressure of light apparently con- 

 firmed hy late experimenters does not realty exist, and that there 

 arises a certain resistance which a reflecting body encounters in a 

 region of radiation, and wmich in the movement of a reflecting 

 body would be shown in the body without a normal component 

 in consonance with the second law of thermodynamics. He sus- 

 pects further that the work for overcoming this resistance is 

 changed into electric currents in the reflecting metal. These 

 currents should be of measurable size. This suspicion was appar- 

 ently confirmed by experiment. He mounted a strong cir- 

 cular disc upon the axis of a solid lathe. This disc had a circular 

 highly-reflecting band which was insulated by dry wood soaked 

 in oil. The band was cut and the two ends were connected to 

 two rubbing insulated contacts and to a sensitive galvanometer. 

 The velocity of revolution of a point on this band was 240-410 

 meters per second. When sunlight fell on the silvered band the 

 thermo-electric effect was only 2*3 mm deflection if the disc was at 

 rest. When the disc rotated in the dark there was no reflection. 

 As soon as sunlight fell on the rotating disc the galvanometer 

 gave a deflection of 42 mm , and this deflection persisted while the 

 sunlight remained. It disappeared when the sunlight was re- 

 moved. When the revolution was reversed the deflection was 

 reversed to — 32 mm . A half speed gave a deflection of 20 mm . 

 These experiments were made in August and September, 1880, 

 in the Technical Institute of Florence, and were so far as is 

 known never resumed. — Beiblatter, Ann. der Phys., No. 22, 1904. 



J. T. 



12. Notes on JC-Light ; by William Rollins. Pp. 400, plates 

 150, Boston, 1904. — This beautifully printed volume contains 

 the arduous researches of a professional man who has devoted 

 his evenings to what is perhaps the most baffling and trying 

 of all physical research, experimentation on gases at low vacuo — 

 trying both to physical endurance and to the spirit ; for just 

 as nature seems to be inclined to open her mysterious chambers, 

 the glass apparatus and the mechanical apparatus employed in 

 producing such vacuo breaks, and the course of experimenta- 

 tion has to be begun anew. The expenditure of time and 

 money, in giving freely to physicians and surgeons the best 

 means of producing and employing the X-rays, shown by this 

 book is remarkable, especially when one reviews the history 

 of the use of these rays and sees the endless effort to secure all 



