478 The approaching Total Solar Eclipse. [Oct., 



parts of Greece and Turkey. And of these regions only those in 

 the Spanish peninsula and Sicily are practically available, because 

 in the others the duration of totality will be less and the sun will 

 have but a small elevation. In Greece, for instance, and Turkey, 

 though the phenomena of totality may chance to be well seen, yet 

 the chance is not such as would justify an expedition from the prin- 

 cipal astronomical centres of Europe. The best places of all for 

 observing the eclipse will undoubtedly be those along or near the 

 track of totality in Algeria. These, however, will probably be left 

 to the astronomers of France. 



Fig. 1 shows the actual presentation of the earth towards the 

 snn, and the course and shape of the moon's shadow on Decem- 

 ber 22nd next. The hour is supposed to be solar noon at Green- 

 wich. The earth must be conceived to be rotating in the direction 

 shown by the arrow (on the equator), and at such a rate that any 

 meridian line in the figure will reach the place occupied by the 

 next meridian towards the right in two hours. The black spot to 

 the west of Spain represents the shadow of the moon at the hour 

 named. This shadow is surrounded by the penumbra, a portion of 

 which, however, remains throughout the eclipse beyond the northern 

 limits of the earth's disc. The course of the shadow is indicated by 

 the curved line taken through the black spot. If an observer on 

 the sun could trace the apparant path of the moon's centre across 

 the earth's disc, he would not find it curved in this way, but appre- 

 ciably straight. As the earth is rotating, however, the disc turned 

 towards the sun undergoes an appreciable change during the dura- 

 tion of central eclipse, and the motion of the different points of the 

 earth along parallels curved like those shown in the figure, causes 

 the path of the moon's centre with reference to the earth's globe 

 (distinguished here from her disc as seen from the sun) to have the 

 shape indicated in the figure. 



Central eclipse begins on the earth generally at twenty-six 

 minutes before noon, — in other words the black shadow shown in 

 the figure as already well advanced is supposed to have entered on 

 the disc twenty-six minutes before the epoch corresponding to the 

 figure. Central eclipse concludes for the earth generally at twenty- 

 one minutes past one, or eighty- one minutes after the epoch corre- 

 sponding to the figure. The total interval during which the moon's 

 shadow (as distinguished from her penumbra) falls upon the earth 

 is thus 1 h. 47 m. ; and the amount of motion due (during this in- 

 terval) to the earth's rotation can be conceived by remembering 

 that the southern extremity of Spain moves during totality from 

 a place below the dark spot in the figure (and on the proper 

 parallel, of course) to about the place occupied in the figure by 

 Sicily. 



It will be evident from a further consideration of the relations 



