170 
POPULAR SCIENCE REVIEW. 
even doubted its real existence, and were inclined to ascribe its supposed 
observation to the effects of atmospheric action. Of late it has been drawn by 
several observers, so that its real existence cannot now be questioned. During 
this year it has been looked for. by Mr. Common with the great 37-inch 
reflector at Ealing. The nebula was seen as a distinct object of con- 
siderable extent, but beyond it, and right within the Pleiades, were discovered 
two others, both long elliptical nebulae of tolerably well-defined form. There 
seems reason to believe, therefore, that the entire background of the Pleiades 
is nebulous. 
Supposed Changes on the Moon. — Two years ago those astronomers who 
take especial interest in observing the Moon were startled by the announce- 
ment by a German astronomer, Dr. Hermann J. Klein, of a remarkable 
change on the lunar surface, due to the sudden formation of a great, black 
crater over three miles in diameter. This new formation was stated to have 
appeared in a comparatively open region of the Moon, near the great valley 
rill of Hyginus. A full accoimt of the early history of this supposed case of 
a real physical change on the Moon will be found in the Popular Science 
Review for April, 1879. The great interest of this announcement lies in the 
fact that according to the opinion generally held by astronomers, all active 
change on the lunar surface had long ere this died away ; though, on the other 
hand, there have been few, if any, of these astronomers who have devoted 
much time to the study of the lunar surface, who have not strongly expressed 
their dissent from this opinion. It so happens that this region near Hyginus 
had been especially well studied, and had been frequently drawn, and not 
only in the past, but within very recent times. It was therefore at once 
recognized that this reported change, if confirmed, would afford a crucial 
confirmation of the view that real changes of great magnitude were still 
occurring on the lunar surface. If this were so, then at any moment the 
lunar surface might present us with the opportunity of studying a great 
volcanic eruption, covering the surface for miles with lava and filling the 
surrounding region with clouds of ashes. Even if no volcanic eruption were 
to take place, at any moment a grand landslip might occur, presenting a 
magnificent spectacle as some great mountain mass rolled crashing down a 
slope, ploughing up the surface before it and raising enormous clouds of debris 
as peak after peak fell with terrific energy into the depths below. There 
could be no doubt that the establishment of a single case of actual physical 
change on the Moon would increase manifold the charm and value of lunar 
observations. 
In the article in the Popular Science Review for April, 1879, the history 
of this supposed new formation terminates with the close of February of the 
same year. At that period it was still uncertain whether any new object 
had really made its appearance in this portion of the lunar surface. That a 
number of observers had seen something in this region was unquestionable ; 
but then others had failed to recognize anything of the kind. The only two 
experienced lunar observers who had seen this region under proper illumina- 
tion, were Dr. Klein, its discoverer, and Prof. Julius Schmidt, the great 
selenographer of Athens. Little was known about the observations of the 
latter, and the former had only seen it properly on one night. Others, 
including more than one who were thoroughly familiar with the region, had 
