F. A. P. Barnard on the Zodiacal Light. 233 
pothesis than before, will in many others, conflict with it even 
more violently. 
It is totally impossible, in short, to admit that the ring can be 
seen at all at midnight, without being forced to require that it~ 
shall be seen spanning an immense arch in the heavens, earlier 
or later in the night. Suppose, for instance, that at the time of 
the midnight observations of the zodiaeal light by Mr. Jones, 
when the columns appeared in his prime vertical and equal to 
each other, there had been an indefinite number of observers 
posted along the great circle of the earth which was coincident 
at the moment in plane with the ecliptic; all of them, there- 
fore, having the ecliptic vertical. We must be permitted to take 
it for granted that the luminous columns visible to Mr. Jones 
would also have been visible to every other such observer, whose 
horizon did not pass above the illuminated substance whatever 
it may be, on the one hand, nor approach so near to the sun as 
to be affected by his light, on the other. And consequently the 
eastern column must have appeared more extended, to observers 
east, and the western, to observers west, than they did to Mr. 
ones. Now if we take an observer among this number, to 
whom the sun was but 18° depressed, and assume that the light 
produced from a ring interrupted by the earth’s shadow, and (in 
the first instance) presenting to one in the position of Mr. Jones, 
only a trace of brightness in the east and west horizons, then 
this supposed observer of ours must have seen the light stretch- 
Ing 158° from the horizon on the side of the sun through his 
zenith, and therefore to a point only 22° above the opposite 
orizon. 
The ecliptic is only vertical in the inter-tropical regions, and I 
remember no records of the phases of the zodiacal light in those 
latitudes, made earlier than those of Mr. Jones. Though I have 
not had the opportunity of examining his diagrams particularly, 
[think Lam correct in presuming that he has recorded no aspect - 
of the light, in which it seemed to pass the zenith. Tn the lati- 
tude of Tuscaloosa, Alabama (334°), I have often observed the 
light when the ecliptic passed within 10° of the zenith, ss 
the length of the column a single degree ; yet I never = 
summit of the brightness approach anywhere near to the meridian. 
Assuming that the light is not a mere luminous éocus, 
moveable laterally, we shall find that it must mae be visible un a 
» Szntes, Vol, XXI, No. 62,—March, 1856. 
