On Increasing the Rigidity of long, thin Metallic Pointers, fyc. 67 



The probable origin of the sun's spots and other questions 

 of solar physics that claim attention must be left for future 

 consideration. I will only remark here that it has long been 

 apparent that the diverse phenomena which occur at the sun's 

 surface are traceable, more or less directly, to the action of some 

 form of eruptive force. The present investigation seems to have 

 led Lo the discovery of the true nature and origin of this force, and 

 at the same time to have revealed the process by which the sun's 

 radiation is maintained, the primary source of the solar heat 

 being doubtless, as now generally believed, the process of conden- 

 sation maintained by the force of gravitation. 



It is worthy of remark, in conclusion, that as comets directed 

 our attention at the outset toward the sun, so the sun, in its 

 turn, leads us back again to our starting-point, since we see 

 that if we transfer to cometary bodies the physical structure we 

 have recognized in the sun's upper photosphere, viz. the exist- 

 ence of a succession of light vaporous envelopes subject to the 

 energetic action of the force of heat-repulsion, the mystery in 

 which some of the curious transformations they undergo have 

 hitherto been involved seems to be in a great degree dispelled. 

 No one doubts that comets are chiefly composed of very light 

 vapours, though some of the larger ones may have a solid nu- 

 cleus. If, as intimated, certain observed cometary phenomena 

 indicate that these vapours, like the solar vapours, are arranged, 

 for a certain d^pth at least, in envelopes which are liable to be 

 greatly expanded, or even wholly expelled by the increasing 

 amount of heat received from the sun, we have in the probable 

 physical structure of comets another indication that these bodies 

 were originally detached from the sun's photosphere, in addi- 

 tion to that furnished by certain features of the cometary 

 motions*. 



VII. On Increasing the Rigidity of long, thin Metallic Pointers, 

 Magnetic Needles, §c. By John C. Douglas, Science Teacher, 

 G.B., E.I. Gov. Telegraph Department^. 



THE needles and needle-indices of galvanometers, when long 

 and (to ensure lightness) thin, are very liable to become bent; 

 or to prevent this bending and admit of the pointer being brought 



other element of a compound substance in the depths of the photosphere. 

 However this may be, it can hardly be doubted that the ascent and de- 

 scent of the solar vapours and the combinations and decompositions going 

 on among them must be attended with disturbances of electric equilibrium, 

 from which decided effects must result. 



* Norton's ' Astronomy,' revised edition, p. 276. 



t Communicated by the Author. 



F2 



