1872.] The Construction of the Heavens. 325 
The discrepancy between the statements in the “ Out- 
lines” and in the “‘ Observations” is so complete that I ven- 
tured to communicate with Sir John Herschel respecting it, 
though I was not without a tolerably definite idea as to its 
origin. He replied as follows :—‘‘I thank you for calling 
attention to that section in my ‘‘ Outlines.” Undoubtedly 
there is a discordance of statements which requires cor- 
rection. But the appeal there” (that is, in the “‘ Outlines’’) 
“is rather to a vague naked eye impression than to the 
statistical result of a¢tual enumeration; and assuredly ona 
cursory view of the heavens on a clear night, stars down to 
the 7th and 8th magnitude do affect the eye, though we 
cannot fix them by reason of that strange law which curtails 
a star directly looked at of a very large aliquot part of its 
photometric effectiveness.” It will be seen that Sir John 
Herschel here maintains at once the reality of the aggrega- 
tion of the brighter stars on the viszble Milky Way, and the jus- 
tice of the statistics which related to the Milky Way regarded 
asa zone. This is undoubtedly the true explanation of the 
matter, as my equal surface chartings have since abundantly 
demonstrated. The brighter orders of stars, down to the 
r1th, do unquestionably crowd upon the real Milky Way,— 
that altogether irregular region of star streams and star 
clusterings which has been aptly compared to a band of 
broken cirrus clouds; but if we lose sight of these irre- 
gularities, if we conceive of the Milky Way as of a uniform 
zone, and take the average distribution of the brighter stars 
over that zone, we no longer find that exceptional degree of 
richness, for the gaps and lacune of the Milky Way are 
as poverty stricken, notwithstanding their position in that 
imagined zone of richness, as the brighter parts are rich in 
respect of these higher orders of stars. But this explana- 
tion shows that the conclusion based by Sir John Herschel 
on the zone-statistics should be not merely abandoned but 
replaced by tts converse. Let the reader carefully re-study- 
it in the light of the above considerations, and he will see at 
once that this is the case. 
The second point to which I would invite attention in Sir 
John Herschel’s work is his discussion of the phenomena 
presented by the two Magellanic clouds. His reasoning 
cannot be too carefully considered. It runs thus :— 
“Taking the apparent semi-diameter of the Nubecula 
Major as three degrees, and regarding its solid form as, 
roughly speaking, spherical, its nearest and most remote 
parts differ in their distance from us by little more 
than a tenth part of our distance from its centre. The 
