SCIENTIFIC SUMMARY. 
305 
of orbit,” as he truly remarks, 11 which has not been shown to exist in the 
case of any binary system.” It may be remarked that Sir John Herschel, 
nearly forty years ago, deduced the period 253 years, while Smyth obtained 
a period of 240 years. In the Monthly Notices for December 1845, Mr. 
Hind gives elements “ entirely differing from those previously computed by 
Herschel and Madler,” the difference being “ materially owing to the great 
influence exerted by recent measures at Mr. Bishop’s observatory by Mr. 
Dawes.” Mr. Wilson’s result involves a somewhat startling advance in the 
same direction. He finds that the apparent orbit is part of an hyperbola of 
eccentricity 2-2. u The real hyperbola may be shown by a graphical con- 
struction to have an eccentricity of 3T6, and its line of nodes nearly coin- 
cides with the axis major.” “ If this orbit is correct, the angle of position 
will decrease to the limit 188°. It is now about 238°T2, according to the 
observations of Mr. Seabroke and myself,” he adds, “ and a little less by the 
interpolating curve— about 237°'85.” 
An Unsuspected Cause of Diffraction Phenomena in Telescopes . — Captain 
Noble makes the following remarks in the Monthly Notices for April : — 
“Some little time ago, in observing Jupiter and his satellites, I remarked 
certain emanations which appeared to have their origin in diffraction. I 
was very much puzzled to imagine in what way these phenomena could 
arise. My 4’2-inch Boss object-glass is simply perfect; my eye-pieces were 
carefully cleaned, and, so far as I could see by removing them, and looking 
up the tube at the Moon or Jupiter, the tube itself was free from any ob- 
struction. Since, however, the general definition of the instrument was 
sensibly unimpaired, I took no further action in the matter, and let things 
take their course until about the middle of last month. I was observing 
the sun one morning at that period, when I removed the eye-piece for some 
reason, and happened to glance obliquely up the tube. To my astonishment 
I saw, brilliantly illuminated by the sun, a perfect grating of excessively fine 
spider-webs, spun vertically across the interior of the telescope, somewhat 
within the focus of the object-glass. A light, in more senses than one, 
suddenly broke in upon me, and I very speedily removed the offending lines. 
I had the pleasure, that same evening, of viewing the Jovian system shorn 
of all optical appendages. I am too ignorant of the Arachnida to be able 
to guess at the species which produces a web of such extraordinary tenuity ; 
but it certainly must be an extremely minute one, not only on account of 
the excessive fineness of the filaments which it spins, but also in order that 
it should have found its way inside of a tube so thoroughly and carefully 
closed as (I should think) to prevent the existence of interstice or aperture 
whatever whereby an entry might be effected.” 
Spectrum of the Zodiacal Light. — In our last Summary we mentioned that 
Liais had found the spectrum of the zodiacal light to be a faint continuous 
one. Before that statement had appeared in these pages, news was received 
from the skilful Italian spectroscopist Bespighi, to the effect that the 
spectrum of the zodiacal light consists in the main of the bright line form- 
ing the chief constituent of the spectrum of ordinary green aurora. 
“ Formerly,” he says, “I made spectroscopic observations on the zodiacal 
light, in the East Indies, but I could not see Angstrom’s line, and I had 
obtained no result because I did not take the necessary precautions, protect- 
YOL. XI. — NO. XLIY. X 
