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 



