1872.] The Construction of the Heavens. 327 
spreading of the stars towards the several parts of the ring, 
this spreading being uniform between the distances corre- 
sponding (according to Struve’s estimate) to the position of 
stars of magnitudes 1 to 6, of 7th magnitude, of 8th, and 
lastly of gth magnitude. It seems impossible to attach the 
slightest weight to the evidence afforded by the resulting 
disc, since the construction of the disc is based on supposi- 
tions (as to the uniform scattering of stars radially towards 
the equator), which are directly contrary to Struve’s own 
clear recognition of a want of uniformity circularly round 
the equator. 
Struve deduced from this imperfect method of reasoning, 
combined with the study of Sir W. Herschel’s star-gauges 
and a theory on the extinction of light, the conclusion that 
the Milky Way is unfathomable in its own level. He consi- 
dered this view to be in accordance with the results obtained 
by Sir W. Herschel in his papers of 1817 and 1818. 
Herschel did not, however, find the Milky Way unfathomable 
all round the central line of the zone, but only in certain 
definite directions—towards the heart, in fact, of certain 
clustering aggregations. Struve misunderstood Herschel’s 
remark that ‘‘ when his gauges would no longer resolve the 
milky way into stars, it was not because its nature is ambi- 
guous, but because it is fathomless,” for he thus renders 
Herschel’s words into French, ‘‘ nous pouvons faire la con- 
clusion que sz nos jauges cessent de résondre la Voi Lactée 
en étoiles, ce n’est point parce que la nature en est douteuse, 
mais parce qu’elle est insondable.” Doubtless he read 
Herschel’s ‘‘ when” as equivalent to the German “ wenn.’’* 
As Sir John Herschel has remarked, disposing thereby at 
once of Struve’s infinite extension theory and of his reason- 
ing respecting the extinction of light, ‘‘We are not at 
liberty to argue that at one part of the galaxy’s circum- 
ference our view is limited as by a sort of cosmical veil, 
which extinguishes the smaller magnitudes, cuts off the 
nebulous light of distant masses, and closes our view in 
impenetrable darkness; while at another we are compelled 
by the clearest evidence telescopes can afford to believe that 
star-strewn vistas lie open, exhausting their powers and 
stretching out beyond their utmost reach, as is proved by 
that very phenomenon which the existence of such a veil 
would render impossible, viz., infinite increase of number 
and diminution of magnitude, terminating in complete 
* Thus is explained what Sir John Herschel and Professor Nichol clearly 
found perplexing, viz., Struve’s conviction that the elder Herschel’s results 
confirmed his own remarkable theory. , 
