Sept., 1905] 



KNOWLEDGE & SCIENTIFIC NEWS. 



217 



example is here given. This is shown in Fig. 4, and 

 was secured on July 14 of last year, and the plates 

 were exposed at iih. 8m. a.m., and i2h. 8m. p.m. 

 respectively. It will be seen that during this interval 

 of about one hour a very decided change of form in the 

 largest prominence has occurred. Instead of the some- 

 what symmetrical shape that existed at the first of 



For very rapid changes of form in individual 

 prominence, that is, changes that occupy only a few 

 minutes of time, the visual method must still be em- 

 ployed, a most convenient form of instrument for this 

 purpose being the Evershed form of spectroscope. 



From the above somewhat cursory account of this 

 spectroheliograph and its first fruits, it is hoped that 



PLATE III.— The Sun as Photographed in "K" Light on August 29, 1904. 



Exposure for Limb 2 h. 40 m. to 3 h. 13 m. Q.Vl.T. (interval 24 m.l. 

 Exposure for Disc 3 li. 16 m. 5 s. to 3 h. 16 m. 30 s. G.M.T. (interval 23 s.). 



these times the prominence is most intense on the left- 

 hand side, and the material appears to be thrown to- 

 wards the right as if acted upon by a strong current. 

 Its height, at the same time, has been considerably 

 increased. The other very intense but smaller 

 prominence has almost disappeared during the same 

 interval. 



some of our more wealthy readers will be induced to 

 take up the work and carry out one or more of the 

 numerous branches of this research which are as yet 

 untouched. Although the initial expense is somewhat 

 costly, the investigation of the sun by this instrument 

 is so full of interest that the labour involved is sure to 

 be well repaid.- 



