230 Dr. Herschel’s Account of , 
how far we have been authorized to ufe the mental eye. This 
being premiled, I may fafely proceed to give my obfervations. 
April 19, 1787, 1 o h. 36'' fidereal time. 
1 perceive three volcanos in different places of the dark part 
of the new moon. Two of them are either already nearly 
extinCt, or otherwife in a irate of going to break out; which 
perhaps may be decided next lunation. The third flaews ail 
actual eruption of fire, or luminous matter. I meafured the 
diftance of the crater from the northern limb of the moon, and 
found it f 57", 3. Its light is much brighter than the nu- 
/ 
cleus of the comet which M. Mechain difcovered at Paris the 
10th of this month. 
April 20, >787, 10 h. 2 / fidereal time. 
The volcano burns with greater violence than lad; night. 
I believe its diameter cannot be lefs than 3", by comparing it 
with that of the Georgian planet ; as Jupiter was near at hand, 
I turned the telelcope to his third fatellite, and effimated the 
diameter of the burning part of the volcano to be equal to 
at lead twice that of the fatellite. Hence we may compute 
that the Alining; or burning: matter mud be above three miles in 
diameter. It is of an irregular round figure, and very fharply 
defined on the edges. The other two volcanos are much 
farther towards the center of the moon, and refemble large, 
pretty faint nebulae, that are gradually much brighter in the 
middle; but no well defined luminous fpot can be difcerned in 
them. Thefe three fpots are plainly to be didinguifhed from . 
the red of the marks upon the moon ; for the reflection of the 
4 fun’s 
