80 
POPULAR SCIENCE REVIEW. 
seemed to differ in appearance from similar stars. This led him to examine 
it with higher powers, when this object was seen to be not really a star, but 
to show an ill-defined bright disc, about 4" in diameter, and of a bluish 
colour. When closely examined it seemed to be surrounded by a faintish 
glow. From Mr. Webb’s description this object must have appeared similar 
to the planet Uranus when seen through a white, hazy mist. On referring 
to the star catalogue it was found to be the object observed as a star by 
Argelander during his survey of the Northern Heavens, and recorded by him 
as No. 4004 Zone + 41°. Its place for the year 1880 is R.A. 21 h 2 m, 5 Decl. 
+ 41° 45'*3. Mr. Webb communicated an account of his observation to Hr. 
Copeland at Lord Lindsay’s observatory at Dun Echt, in Aberdeenshire, 
who took the first opportunity of observing this object with the fine 15-inch 
refractor belonging to the observatory. According to Dr. Copeland this 
object is not quite circular, and has a sharp nucleus near its north preceding 
edge, and a faint diffusion of fight on its opposite direction. It is, therefore, 
an exceptionally compact and bright planetary nebula. When examined 
with the spectroscope it gives three bright fines, one far brighter than the 
others, and these bright fines agree well in position with those found by 
D’ Arrest to be generally given by nebulae of this description. 
Solar Parallax from Meridian Observations of Mars . — In the ‘ Observa- 
tory,’ for November, 1879, Mr. A. M. W. Downing, of the Royal Observa- 
tory, Greenwich, has calculated the value of the solar parallax which results 
from the meridian observations of Mars made in the summer of 1877 at the 
observatories at Leyden and at Melbourne. Comparisons were only made on 
days when Mat's and the comparison stars were observed at Melbourne, 
either on the same day as at Leyden, or on the following day. Twenty- 
nine corresponding sets of observations were obtained, and from them the 
solar parallax was computed. The separate results range between 8" - 65 and 
9 /A 39, and when properly combined, give as the final result : — 
Mean solar parallax = 8 //- 960 ± 0"*051. 
Mr. Downing remarks , 1 In the fight of recent researches on the subject, 
we must, I suppose, consider this value of the solar parallax to be too large ; 
it is, however, to be remarked that Professor Winnecke obtained the value 
8"*96, and Mr. Stone that of 8' /# 94, from meridian observations of Mars in 
1862 ; and though Professor Newcomb’s discussion gave the result 8"'8 55, 
still, as Mr. Stone has pointed out, the smaller value depends chiefly on the 
use of the Santiago observations, which he declares to be inadmissible. It 
appears, therefore, that from meridian observations of Mars we get a parallax 
of not less than 8"*9 ; and we are almost forced to the conclusion that there 
is something in the method , which persistently tends to give a large result ; if 
this be so it introduces another very perplexing element into researches on 
solar parallax.’ 
On examining the separate results given by Mr. Downing, it would appear 
that there is some trace of systematic error in the observations or in their 
reduction. Thus, as the result of the fourteen separate determinations deduced 
from observations made before opposition, we have a solar parallax of approxi- 
mately 9"‘037, whilst as the result of the fifteen separate determinations 
deduced from observations made after opposition, we have a solar parallax of 
