242 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



This conclusion essentially confirms that of J. W. Draper, 

 published more than thirty years ago. 



3. Interference and Polarization. 



Lockyer lias suggested the use in the solar eclipse of July 

 29 of a Rutherfurd reflection grating in place of prisms for 

 the purpose of observing the corona, using the coronal atmos- 

 phere in place of a slit. To test the question, he construct- 

 ed an artificial eclipse by means of a circular aperture two 

 inches in diameter, cut in card-board and placed thirteen 

 yards distant from a 3-J-inch telescope, the circular slit be- 

 ing illuminated by a parallel beam of electric light. Some 

 distance short of the focus of the telescope the grating was 

 so placed as to throw the spectra of the circular slit on the 

 photographic plate, and then photographed for the first, sec- 

 ond, and third orders on one side, the slit being illuminated 

 with, sodium and with carbon vapor. The third-order spec- 

 trum gave in forty-two seconds a photograph showing the 

 rings due to the carbon vapor flu tings. Hence he thinks the 

 third-order spectrum of the eclipse may be photographed in 

 at least four minutes, the second order in two, and the first 

 in one minute. This suggestion was anticipated by Henry 

 Draper, who had constructed his phototelespectroscope on 

 the above plan some months before the paper of Mr. Lockyer 

 was presented to the Royal Society. 



IT. Draper, in a note to Nature, states the results of some 

 of his investigations relative to the position of the oxygen in 

 the sun's surface. Using for the purpose one of Mr. Ruther- 

 ford's exquisite silvered glass gratings of 17,296 lines to the 

 inch, giving a dispersion equal to that of twenty heavy flint 

 glass prisms, attached to. his 12-inch Clark refractor, the full 

 aperture being employed, and placing in front of the slit the 

 terminals of an induction coil, by which a strong oxygen spec- 

 trum was obtained in the same field, lie was entirely unable 

 to perceive that the lines of oxygen visible in the spectrum 

 of the solar disk projected beyond the visible limb of the sun. 

 In other words, they could not be detected in the base of the 

 chromospheric layer. 



Adams has presented to the Physical Society of London a 

 new form of polariscope suitable for projecting on a screen 

 the figures formed by any crystal, and for measuring the 



