78 NOTES ON THE 



FIG. 21. 



RETICULATED NEBULA. 



often seen, when the sky is quite clear, all the large 

 stars above the seventh magnitude surrounded with 

 photospheres of 2' or 3' or more in diameter, precisely 

 resembling that about the finer specimens of nebu- 

 lous stars." Do these photospheres consist of luminous 

 points or stars, though yet unresolvable by our best 

 telescopes, each photosphere being a portion of that 

 firmament of stars to which, as we suppose, each 

 star or system of stars is destined to give birth ? 



136. If the planets cease not to increase in 

 density, will they at length become incandescent ? 



137. Do self-luminous stars within determinate 

 distances repel each other ? but beyond those dis- 

 tances, have they a tendency to gravitate toward 



