Si 
remarkably porous, so that even a heavy rainfall is soon swallow- 
ed up and lost. 
These facts have too often been lost sight of in discussions of 
Hamakua, but it is obvious that where the rocks and soil of a 
district are so pervious as to make stream flow possible only 
during heavy rains, arguments for the protection of the drain- 
age basin lose their force. In other words, to secure a regular 
flow there must be an impervious stratum to catch the water and 
gather it into certain channels, where later it can be turned' to 
account by man. The known facts do not justify the statement 
that a dense forest cover in Hamakua would have no influence 
on stream flow, but they surely do show that Hamakua is in a 
very different case from Hilo. 
Furthermore, it should be noted that the construction of the 
Hamakua Ditch, which brings out water from the Kohala Moun- 
tains, has materially relieved the water situation in Hamakua, 
not only by assuring a supply of water for fluming the cane, but 
also by permitting the irrigation of lands that have heretofore 
had to depend on rainfall. 
Another beneficial influence of a forest cover is that it prevents 
erosion. In Hamakua the situation where most benefit from 
such protection would be derived is, unfortunately, in the home- 
stead belt, where the land has already passed into the possession 
of small individual owners. It is indeed true of the whole ques- 
tion of water shed protection in Hamakua that the lands where it 
would be of most value are no longer controlled by the Govern- 
ment. 
Influence of the Forest on Climate. 
One of the strongest arguments for a forest reserve in Hama- 
kua is based on the beneficial influence that a forest belt of suffi- 
cient size is supposed to exert on the climate of a district, particu- 
larly in regard to inducing precipitation. The gist of the argu- 
ment is as follows : 
To insure rainfall the first requirement is winds bearing mois- 
ture-laden clouds. In Hawaii this condition is met by the trade 
winds. In the Hilo District and on the Kohala Mountains a 
mountain rises in the path of the clouds ; stops them ; precipita- 
tion ensues ; result, a district of heavy rainfall. In Hamakua 
a different topographic situation prevails. Instead of a moun- 
tain mass in the path of the trade wind clouds there is the de- 
pression between Mauna Kea and the Kohala Mountains, too low 
in elevation to stop the moisture-laden clouds, which accordingly 
pass on to be dissipated over the open, dry plains of Waimea, or 
to go on out to sea again over Kawaihae Bay. So far a state- 
ment of fact. Now, so runs the argument, were there a suffi- 
ciently large belt of forest at the northeastern edge of the Wai- 
mea, Plains, such as formerly existed between Mana and Mud 
