202 
SCIENTIFIC SUMMARY. 
ASTRONOMY. 
A WINTER of sucli peculiar and continuous obscurity could not be 
expected to testify to much astronomical progress as far as observation 
is concerned. From Mr. Gledhill's analysis of the weather, recently com- 
municated to the “ Astronomical Register,” it appears that at Mr. Crossley’s 
observatory, near Halifax, there were 2 very fine, 9 good, 22 fair, and 21 
bad nights during the year 1875 ; and matters have certainly not been mend- 
ing since in England. We can only hope that observers in other parts of 
the world may have been more favoured. 
The Sun has continued in a very undisturbed condition, though one large 
spot, visible to the naked eye, was reported in February, which may be the 
precursor of renewed activity. From an ingenious method of registering 
isothermals on the sun’s disc by the blackening of the double iodide of 
copper and mercury, Professor Mayer has been led to the conclusion that 
areas of uniform temperature exist on the sun’s surface, the position of 
which is subject to continual variation. Professor Langley thinks that the 
light of the dark nuclei of solar spots equals at least 5,000 times that of the 
full moon. 
Venus . — This beautiful planet has been gradually increasing in brilliancy 
and altitude, and is now in a very good position for observation. On several 
occasions during the present season Mr. Dennett has distinctly traced spots 
on her disc with a 2|-inch achromatic ; and on Feb. 29 the present writer 
was able to confirm their existence with a powerful silvered-glass reflector ; 
though they were' so faint that they would have escaped any cursory 
examination, and could not have been delineated. It is very desirable that 
more attention should be paid to this body, so conspicuous, so near, and yet 
so little known. 
The Moon . — A new and important work on our satellite may be expected 
from Mr. Neison, who has for some time paid much attention to seleno- 
graphy. He has taken very accurate micrometrical measures of the 
position of 35 points on the lunar surface, with a view to rectify the deter- 
mination of the equator and first meridian. These include 4 previously 
measured less correctly by Lohrmann and 4 by Miidler. 
Mars . — Five drawings, taken in June and Aug. 1875, by Holden, with 
the 26-inch Washington achromatic, power 400, have been presented to the 
