354 THE POPULAR SCIENCE MONTHLY. 



therefore " the supposition of the existence of this liglit in the plane 

 of the sun's equator does not satisfy the observations made." The 

 closing sentence of his very interesting article gives the first intima- 

 tion that the zodiacal light has a near connection with our globe. 

 Housseau says: 



" One is struck, wittiout doubt, with the near approach, which our elements 

 show, between the line of nodes of the zodiacal light and that of the nodes of 

 the terrestrial equator upon the ecliptic. This circumstance, as far as it is veri- 

 fied, may help to explain the causes of this luminous phenomenon causes which 

 are, it may be, more local than has hitherto been supposed." 



This notice is the only one, of any importance whatever, that was 

 taken of the zodiacal light for many years, with the exception of 

 some experiments made to ascertain whether there is any heat con- 

 nected with it experiments which we think resulted in establishing 

 the fact that it is near enough to emit heat sufficient to affect a ther- 

 mo-electric pile of twenty-five pairs, causing the needle of the galva- 

 nometer to indicate 12 when the pile was directed toward the base 

 of the zodiacal light. 



We come now to a consideration of the observations taken dur- 

 ing the cruise of the Japan Expedition, and we hope our readers 

 are not weary of the subject ; for, if it can be demonstrated that 

 we have a ring of nebulous matter around our globe at a distance of 

 150,000 to 200,000 miles, there are many inquiries growing out of 

 that fact full of interest, and yet to be answered by experiment 

 and induction. It will be a matter, then, to be considered whether 

 it is self-luminous that is, of the nature of the sun's photosphere 

 or whether it shines only by reflected light, like the rings of Sat- 

 urn ; whether it is increasing or diminishing in magnitude and ex- 

 tent. If it is shown to be self-luminous, we will then wish to know 

 whether it may not be widening and extending itself, at the same time 

 increasing in its capacity to emit both light and heat, until it envelops 

 the entire globe, modifies climate, melts the icebergs and snows of 

 northern latitudes, and dispels darkness from our globe. We may 

 inquire, too, whether it may not be used as a grand instrument in the 

 hands of the Creator for the future development of his purposes in 

 regard to our globe. It may also be an inquiry whether it does not 

 already influence the magnetic state of the earth, and play an impor- 

 tant part in the cal^ses producing the aurora borealis. These and 

 many more similar questions will arise from the establishment of the 

 fact that the zodiacal light emanates from a ring of nebulous matter 

 so near our earth. Let us, then, give our author a close examination 

 and a patient hearing, that we may be enabled to form a correct judg- 

 ment as to the truth of his deductions. 



We have not space to present all the reasoning by which our author 

 shows that the zodiacal light cannot be produced by a ring of nebu- 



