Scientific Lectures. 139 



teen days thereafter, as he says, a perpetual eclipse. Just after his 

 description of the method reached the secretary of the French 

 Academy, a communication was received from the English astronomer 

 Lockyer, also announcing a similar method. Thanks to these gentle- 

 men, we can now observe the protuberance daily. By such investi- 

 gations it has been shown that they are merely local accumulations 

 of a layer which entirely surrounds the sun, and which is called the 

 " chromosphere." They mostly consist of hydrogen, though sodium 

 and magnesium, and a new non-terrestrial elements — called by 

 Frankland "Helium," and by Yonng " D 3 -stufF," from its character- 

 istic line — have been observed in them. Their motion is oftentimes 

 very rapid ; Professor Young has just observed the explosion of one 

 of these masses, and he saw the fragments rise 100,000 miles in ten 

 minutes ! Their forms are very variable ; says Professor Lockyer : 

 " Here, one is reminded by the fleecy, infinitely delicate cloud-forms, 

 of an English hedge-row with luxuriant elms ; here, of a densely 

 intertwined tropical forest, the intimately interwoven branches 

 threading in all directions, the prominences gradually expanding as 

 they mount upward, and changing slowly, almost imperceptibly." 



[The phenomena of an eclipse was illustrated on the screen by an 

 ingenious slide devised by President Morton. The sun with its 

 spots became gradually obscured as the moon slowly crept over it, 

 until the last ray of light disappeared, and the glory of the eclipse, 

 with its protuberances and corona, flashed into view. Photographs 

 of the eclipses of 1868, 1869 — so excellently observed in our own 

 country — and of 1870 were exhibited, showing the arrangement of 

 the protuberances. A series of these sun-flames, observed by Respighi, 

 and a representation in miniature of the production of a sun-flame, 

 were thrown on the screen. With the induction coil a series of 

 tubes containing hydrogen were illuminated, to show the color of the 

 rosy flames composed of this substance.] 



Among solar phenomena none are of more interest than those of 

 the spots. They are cavities in the luminous portion or " photo- 

 sphere " of the sun. They are often of vast size, sometimes having 

 a diameter of 147 seconds, or nearly nine times that of the earth. 

 The surface of the sun is euriously mottled, resembling a mass of 

 cumulous clouds. Some days before the appearance of a spot these 

 photospheric granules become violently agitated, feculae or bright 

 spots and streaks are seen, and the umbra or nucleus of the spot 

 appears. The penumbra, or half-shade, gradually becomes visible, 

 and assumes a more regular form in proportion to the circular charac- 



