2 TURNElR, Total Solar Eclipses. 



made in 1868, independently by two observers, Janssen 

 and Lockyer. They found that its spectrum was made 

 up of distinct bright hnes — special and very definite 

 colours, that is to say — and by making use of this know- 

 ledge it has since been found possible to see this inner 

 envelope in full daylight without a total eclipse. More 

 recently a new instrument, the spectro-heliograph, has 

 been invented which enables us, following out this same 

 principle, to pJiotogj-aph the Chromosphere, as well as other 

 portions of the sun's surface, of which we had practically 

 no knowledge a few years ago. But although many 

 attempts have been made to detect in similar ways the 

 Corona or any part of it, they have up to the present 

 resulted in failure, and a total eclipse remains unique as 

 an occasion for studying a most important part of the 

 sun, viz., all that out-lying portion of many times his own 

 diameter which we call the Corona. 



It must not be thought, however, that partial eclipses 

 are of no value ; they afford us opportunities for very 

 accurate measures of the relative places of the sun and 

 moon, and this at a time when we ordinarily cannot well 

 observe the place of the moon ; for when the moon is 

 nearly " new," it is during the daytime lost in the sun's 

 glare, and near sunrise or sunset is so low in the sky that 

 other troubles arise. Even without accurate measurements 

 (such as we can now make, but which thousands of years ago 

 were undreamt of), a mere record that an eclipse took place 

 is sufficient, if trustworthy, to give us valuable information 

 as to the motion of the moon, or of the earth in its orbit 

 round the sun. There have indeed been found difficulties 

 in interpreting many of these old records, difficulties so 

 great that of late years it has been doubted whether the 

 records are trustw^orthy enough for this purpose. Ideas 

 of accuracy have no doubt changed in the thousands of 



