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of different observations are so discordant, that the phe- 

 nomenon is still a great mystery. Accordingly at the last 

 eclipse it was studied in every way that human ingenuity 

 could devise. Some observers simply examined it with 

 the naked eye, estimating its shape, structure, and extent. 

 Some used telescopes of varying size for the same pur- 

 pose. Others confined their attention to particular por- 

 tions only. The resources of the physical laboratory 

 were brought into full use. Its light was examined with 



o o . 



spectroscopes and polariscopes. Mr. Edison invented a 

 special instrument called a tasimeter to measure its heat ; 

 it was successful in showing the presence of heat, but 

 being adjusted too delicately, since the inventor did not 

 know how much heat to expect, the index was thrown 

 beyond the limits of the measuring scale, so that the 

 amount of heat was not determined. The best photo- 

 graphic skill was also employed, and the corona which 

 was first photographed in 1869 was again successfully 

 photographed, the times of exposure varying from two to 

 one hundred and sixty seconds. The camera was also 

 used in combination with the spectroscope and polari- 

 scope, and Dr. Draper succeeded in photographing the 

 spectrum of the corona, which had never been done 

 before. 



The polariscope enables us to determine at least par- 

 tially whether the corona shines with its own or with 

 reflected light. The explanation of the phenomenon of 

 polarization is briefly this : "VVe can imagine that through 

 a beam of light coming directly to the eye, planes are 

 passed in every direction, the ; beam of light being the 

 common axis for all the planes. If however the light 

 does not come directly to the eye, but is reflected from 

 some surface, it is no longer possible to pass planes in 

 every direction through the reflected beam ; for the vibra- 



