THE MOON’S FACE. 
247 
activity. Had the terrestrial craters of all periods been ex¬ 
empt, like those of the moon, from atmospheric and aqueous 
attack, it is easy to imagine that they might now be equally 
abundant. 
In comparing the sizes of craters on moon and earth, it is 
impossible to consider general averages, because the size of 
the moon’s smallest is not known; there is so great a multi¬ 
tude close to the limit of telescopic vision that we can readily 
believe there is another multitude beyond. Onty the max¬ 
ima can be compared. The largest known terrestrial crater 
has a diameter of about 15 miles; the largest lunar crater, 
that whose rim is partially preserved in the Carpathian-Ap- 
ennine-Caucasus chain of mountains, had a diameter of 800 
miles. The ten largest terrestrial craters of which I have 
record have a mean diameter of 11 miles;* the mean for 
the ten largest lunar craters is 275 miles.f The ratio of the 
largest is as 53 to 1; the ratio for the ten is as 25 to 1. The 
* (1) The old crater containing Lake Bombon, Isle of Luzon, is mapped 
(Reclus) as 16x14 miles in extent. (2) The crater of Asosan, Isle of 
Kiushiu, Japan, is 15 miles across (Milne). (3) Scrope mentions a “ cir¬ 
cular crateriform lake, about 15 miles in diameter” in northern Kam¬ 
chatka (Volcanoes, 2d ed., London, 1862, p. 457). (4) An imperfect crater 
cirque on Mauritius, mentioned by Charles Darwin, is mapped (Admi¬ 
ralty) as about 15 x 11 miles in extent. (5) The crater walls surrounding 
Lake Bolesna, Italy, are mapped as 11x9 miles across. (6) The extent 
of the crater containing Lake Maninju, Sumatra, is mapped (Reclus) as 
15x7 miles. (7) The extent of the explosion crater of Pepandayan 
(Junghuhn. cited by Scrope) is 15x6 miles. (8) The ancient crater of 
Teneriffe has a smaller diameter, variously cited as 7 and 8 miles and 
variously mapped as 7 and 10 miles. The larger diameter exceeds the 
smaller by 40 per cent. (9) The crater of Deception Island i S. Shetland) 
is mapped as 8x7 miles in extent. (10) The basal rampart of Monte 
Cavo, Italy, is 7 miles across. Certain maps indicate a basal rampart, 9 
miles across, about Mt. Marindin, Isle of Mindanao, and a similar rampart, 
10 miles across, about Mt. Askia, Iceland, but confirmatory literature has 
not been discovered. 
t Apennines, Serenitatis, Crisium, Humorum, Humboldtianum, Bailly, 
Iridum, Clavius, Otto Struve, and Grimaldi. I have some doubt as to the 
propriety of including Mare Humorum, and less doubt as to the omission 
of Mare Tranquilitatis and Mare Fecunditatis. The mean diameter of 
each crater was used in the computation. 
