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POPULAR SCIENCE REVIEW. 
are doubtless aware, Argelander has included all stars down to 
magnitude nine and a-half, within ninety-two degrees of north 
polar distance — the two degrees south of the equator being 
added in order to facilitate the comparison of the northern 
atlas with charts forming the southern survey, one day to be 
completed (it may be hoped) at southern stations. In all there 
are 324,198 stars. All these I have carefully copied in, upon 
a circular chart two feet in diameter, isographically divided 
(in pencil) by radial lines and circles, into spaces extending 
one degree in declination and one degree in right ascension 
for sixty degrees to the north of the equator, the nominal ex- 
tension in R.A. being correspondingly increased with proximity 
to the pole. In fact, all the spaces in Argelander’s series of 
charts (some 26,400 in all) were represented in pencil in my 
projection, before a single star was charted in. Then the stars 
were carefully copied in, space by space, from Argelander’s 
atlas ; at such a rate (on the average), that the whole work of 
charting occupied me about 400 hours.* I do not think that 
the labour was thrown away, when it is remembered that, as a 
result, the statistical distribution of all the stars down to the 
9Jth magnitude was presented to the eye. The gauges 
of the Herschels had included in all about 160,000 stars, and 
Struve, in the elaborate series of inquiries on which he founded 
the theories propounded in his 4 Etudes d’Astronomie stellaire,’ 
dealt with about 32,000 stars ; but the labours of Argelander 
enabled me not merely to count, but to delineate, 324,198 stars 
— not merely to draw inferences from statistical enumeration 
as to the real laws of stellar distribution, but to exhibit those 
laws of distribution to the eye. 
Now the first and most important conclusion deduced from 
this process of charting relates to the Milky Way ; and it will 
be well to defer the consideration of that conclusion until I 
come to speak of the Milky Way as itself a vast conglomera- 
tion of star streams and star sprays. 
But another conclusion, not obviously deducible from the 
chart itself, or its photographic reductions, was forced upon me 
in a very marked manner as the work of charting proceeded. 
Again and again I had occasion to notice the tendency of the 
* Argelander and his assistants were engaged no less than seven years 
and one month in completing their magnificent contribution to uranography. 
The rate at which I copied in the stars was such as to enable me to copy 
carefully within each space on my projection the stars shown in the corres- 
ponding space in the large atlas. It is worthy of notice that a single second 
of extra time (on the average) per star would have caused an addition of 
ninety hours’, or say ten days’, work. The time actually employed on the 
average was slightly less than four and a half seconds per star. 
