seen in the dark Part of the Moon. 431 
I mentioned this soon afterwards to a gentleman of my ac- 
quaintance, who sometimes amuses himself in the study of as- 
tronomy; he was extremely inquisitive about it, and conjec- 
tured this phcenomenon to be some great volcanic convulsion 
in the moon, which induced me at that time to assist my me- 
mory with a sketch like what I have here sent you. I shall be 
obliged to you, Sir, if you will favour me with Dr. Maske- 
lynes opinion, if what I have related is sufficient ground for 
him to form an opinion upon ; and whether any such pheno- 
menon has ever before been observed. When I was lately in 
town, I mentioned the particulars to my worthy friend Mr. H. 
Repton, and if my engagements would have permitted, he was 
desirous I should call with him upon Dr. Herschel, with whom 
he has some acquaintance. 
I am, &c. 
Norwich > WILLIAM WILKINS. 
17th April, 1794. 
To the Rev. Samvel Vince. 
LETTER II. 
REVEREND SIR, Norwich, 2d May, 1794. 
I am favoured with your letter of the 1st instant, respecting 
the description of the light spot observed by me in the moon. 
I am certain as to the evening I saw the phenomenon, be- 
cause I made the memorandum in a pocket journal I keep; 
besides, another local circumstance convinces me of its being 
on a Friday, and not on any other day than the 7th of March. 
Your are undoubtedly right in supposing I had forgot how 
near the moon was to a half moon ; and when I wrote to Mr. 
Vince, I answered him in haste; for his letter to me requested 
