102 JOURNAL OF PROCEEDINGS. 
quarter of a mile in diameter, which, in the course of a couple 
of years gradually increased to a mile and one half. Although 
still visible, its diameter has now shrunk to three-quarters of a 
mile.” It is only fair to say that although the change previous 
to 1866 is now generally admitted, yet Dr. Klein, of Cologne, 
strongly queries any changes since that date. Just imagine a 
crater six or seven miles in diameter and a thousand feet deep 
being wiped out of existence and replaced by a mere pimple. 
Is a globe dead which can still, on occasion, exhibit such powers 
of destruction and reconstruction? 
Our next evidence comes from the observers of the rills 
and clefts on the Moon. Sometimes a rill has been seen 
easily, and on. other occasions, under similar illumination, ap- 
pears to have utterly vanished. What could cause this? It 
may not be unreasonable to suppose that vapors or exhalations 
accumulating between its rocky walls may have temporarily ob- 
secured it, as rolling mists might hide a river from the sight of a 
daring aeronaut floating high in the air. Then again a new 
cleft has been found in a much studied formation which ap- 
peared to have totally escaped the ken of earlier observers who 
had noted much finer and more elusive details. The delicate 
cleft joining the Ariadzeus and Hyginus rills just north of 
Agrippa is an example of an elusive feature, and a fine cleft on 
the northern part of the floor of Mersenius was discovered by 
Elger in 1883, though at that time much more easily seen than 
finer details which had been mapped by earlier selenographers. 
Another apparent case of change is that of Hyginus N., 
though as the evidence of one man only supports the assump- 
tion, many see fit to remain sceptical. Dr. Klein had studied 
the region of Hyginus for twelve years, and. yet on May 27th, 
1877, he discovered a dark depression a few miles northwest of 
Hyginus. Since then the spot, which is by no means a difficult 
object, has been much studied, and its present existence is un- 
doubted, whatever we may think, of its alleged recent birth. 
The greatest contributions to the new selenography, the 
study of the evidences of change, have been made by Prof.W. H. 
Pickering, who in 1891-2, at Arequipa, and since then in Jamaica 
