December, 1913. 



KNOWLEDGE. 



445 



From a photograph by J H. Worthington. 



Figure 521. Flash spectrum obtained near Ovar, Portugal, 1912, April 17th, during a total solar eclipse, with a prismatic 



camera consisting of a 2-1 inch Achromatic Quartz and Rock-salt lens of 50 inches focus with two 50° Quartz prisms in 



front of it. Exposure, about ^-second. The photograph from which this is taken is unique. 



(See " Knowledge," November, 1913, page 408.) 



Figure 522. An enlargement of a portion of the flash spectrum shown in Figure 521. 



From spectrograms taken with a 2-prism flint spectroscope by F. H. Hills, Fulgaon, India, January 22nd, iSqS. 



Figure 523. A'' and Bf, spectra showing the flame bands of the reversing layer of the Sun seen during an eclipse. 

 Compare the definition and straightness of the lines in these spectra, photographed through a slit, with the circles in 



Figures 521 and 522. 



* At point of second contact, t At point of third contact. 



