Three Volcanos in the Moon . 231 
fun’s rays from the earth is, in its prefent fituation, fuffi- 
ciently bright, with a ten-feet refle&or, to fhew the moon's 
fpots, even the darkeb of them : nor did I perceive any fimi- 
lar phenomena lad; lunation, though I then viewed the fame 
places with the fame inbrument. 
The appearance of what I have called the actual fire or 
eruption of a volcano, exactly refembled a fmall piece of 
burning charcoal, when it is covered by a very thin coat of 
white afhes, which frequently adhere to it when it has been 
fome time ignited; and it had a degree of brightnefs, about as 
brong as that with which fucli a coal w r ould be feen to glow 
in faint daylight. 
All the adjacent parts of the volcanic mountain feemed to be 
faintly illuminated by the eruption, and were gradually more 
obfcure as they lay at a greater dibance from the crater. 
This eruption refembled much that which I faw on the 4th 
of May, in the year 1783; an account of which, with many 
remarkable particulars relating to volcanic mountains in the 
moon, I fhall take an early opportunity of communicating to 
this Society. It differed, however, condderably in magnitude 
and brightnefs; for the volcano of the year 1783, though 
much brighter than that which is now burning, was not nearly 
fo large in the dimendons of its eruption : The former feen in 
the telefcope refembled a bar of the fourth magnitude as it 
appears to the natural eye; this, on the contrary, fhews a 
vidble difk of luminous matter, very different from the fpark- 
ling brightnefs of bar-light. 
WILLIAM HERSCHEL. 
Slough near Windfor, 
April 21, 1787. 
P. s. 
