220 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH Ser. 
During the year our party remained on the islands there 
were nineteen rainy days at sea level, eleven of which were 
during the months of January, February, and March, and it 
was only during these months that the rains were heavy enough 
to make the ground muddy. During the remaining months of 
the year the days on which there was rain at sea level were 
distributed as follows: April one, June one, July three, Sep- 
tember two, and December one. None of these rains were 
heavy, being more in the nature of light showers of short dura- 
tion. These observations were taken at different places on the 
islands, but they probably represent approximately the condi- 
tions at sea level on any one island during this time. They do 
not include days on which there were but slight sprinkles of 
rain or mist. 
There were no very heavy rains at sea level during the entire 
year, but heavy rains must occur here at times, for many of the 
valleys show considerable erosion. The dry beds of streams 
are often covered with water-worn boulders, showing that at 
some time the streams have carried a considerable amount of 
water. Furthermore the sides of many of the tufa craters are 
deeply furrowed with gullies, and have much the general 
appearance of steep hillsides in a country of frequent heavy 
rains. The people who live on Chatham Island told us that 
1906 was an exceptionally dry year. There was no rain on this 
island from March until July, in consequence of which much 
of the vegetation was dried up even on the highest parts of the 
island around 2100 ft. elevation. Similar parched conditions 
were noticed on the upper part of Charles Island during the 
months of May and June. 
Heavy dews, as well as a considerable amount of mist, often 
occur at sea level during the spring months. We were anchored 
at Tagus Cove, on the west side of Albemarle Island, during 
the greater part of the month of April, and during this time the 
late nights and early mornings were so misty that any article 
left exposed over night would usually be quite wet in the 
morning. The mist would clear away soon after sun-rise, and 
the remainder of the day would be clear. 
The places where precipitation is great enough to support a 
mesophytic vegetation, are mostly confined to the middle and 
upper parts of the islands. The moisture here is derived from 
