466 SCIENTIFIC RECORD FOR 1884. 



limator a small image of the solar disk is projected by means of an 

 acliromatic lens of 10 or 12 inches focus. On causing now this lens to 

 oscillate rapidly two or three times per second, so as to bring the two 

 opposite edges of the disk alternately on the slit, the lines of solar ori- 

 gin oscillate with the lens, while those which are telluric remain fixed. 

 Moreover, a singular illusion appears : the trembling lines seem to stand 

 out in rehef, ^ud to oscillate in front of the fixed ones. By means of 

 this neat device the author has determined the group a to consist of 

 three entirely distinct sets of lines : first, those which are solar, and of 

 which twenty-five are figured; second, those which are due to the dry at- 

 mosphere (the structure and grouping of these lines strikingly recalls 

 that of the groups A and B ; and since Egoroff has shown these latter 

 to be due to oxygen, it is probable that the former are due to the same 

 element); and, third, lines due to aqueous vapor, of which only a few are 

 given. {J. Phys., March, 1884, II, in, 109.) 



Thollon has also • described and figured with minute accuracy the 

 seventeen lines which constitute the group B of Fraunhofer, arranging 

 them in four sections : First, when the sun is at 80° from the zenith ; sec- 

 ond, when the sun is 60° from the zenith, air damp ; third, when the sun 

 is 60° from the zenith, air dry; and, fourth, lines not of telluric origin. 

 Egoroff's discovery that this group is due to oxygen mainly, disposes of 

 most of the lines. The others are due to solar absorption and to atmos- 

 pheric moisture. {J. Phys., October, 1884, II, in, 421.) 



Egoroff has exhibited before the physical section of the Eussian 

 Physico- Chemical Society the production of the Fraunhofer lines A and 

 B by passing the rays from a calcium light through a layer of dry oxy- 

 gen 20 meters long, under a pressure of 8 atmospheres. (J. Phys., Oc- 

 tober, 1884, II, HI, 467.) 



Liveing and Dewar have investigated the production of spectrum 

 lines of the metals developed by exploding gases. Observing the flash 

 of a mixture of oxygen and hydrogen gases, exploded in a Cavendish 

 eudiometer, in the spectroscope, the authors were struck with the bright- 

 ness of the lines not only of sodium but also of calcium, and were thereby 

 led to make a series of experiments in iron tubes, half an inch in diameter 

 and 3 feet long, closed at one end by quartz plates held in place by 

 means of a screw-cap. The stronger iron lines were distinctly seen, 

 and so various substances in powder were introduced into the tube. 

 In the case of lithium, when the mixture was fired at the remote end of 

 the tube, so that the flame traveled toward the slit, the red line was re- 

 versed, a fine dark line being visible in the middle of the band ; thus 

 proving that there are gradations of temperature in the flame, the front 

 of the advancing wave being somewhat cooler than the following part. 

 Sixty iron lines in the indigo, violet, and ultra-violet developed in this 

 way were photographed. Other metallic salts were introduced into the 

 tube, and also other gaseous mixtures. {Phil. 3fag., September, 1861, V, 

 XVIII, 161 ; Nature, April, 1884, xxix, 614.) 



