232 The Philippine Journal of Science 1921 
under the conditions involved, and that was applied. It con- 
sisted in making the slopes less steep by removing material from 
their upper parts until the balanced pressure at the foot of the 
slope became less than the crushing or deforming strength of 
the rock. In other words, the slopes were brought down to the 
angle of repose. 
This was recently well illustrated at Eugene, Oregon, where 
both the formation (weathered basalt) and the rainfall simulate 
tropical conditions. A hillside of this material, becoming sat- 
urated with rain water, started to slice off, slide, and flow under 
a large lumber mill at the bottom of the slope, bulging the latter 
upward, completely throwing it out of alignment and even 
threatening the structure. The simple expedient of sluicing 
at the foot of the slide solved the difficulty and the material 
of the hill was brought to such an angle that it no longer moved. 
Artesian water.—In view of the fact that a great many people 
have a hazy notion of what an artesian well is, the term is here 
defined. An artesian well is a type of well first bored, as far 
as we know, in Artois, France, and when the word artesian is 
correctly employed we mean a deep well from which water 
flows above the mouth under more or less pressure. This 
pressure is due to the peculiar geological conditions obtaining 
in the locality. Ordinary, shallow, dug wells are not artesian. 
The principles governing the concentration and movement of 
ground water are now well understood; but, at the risk of rep- 
etition, the writer will make a few general statements. 
Although we do not see it, the sea of underground water is 
almost as extensive as, and in some ways more important than, 
the ocean. All the rocks, varying in degree of saturation, con- 
tain water down to limiting depth. Some of this water is found 
in the large trunk channels, joints, and faults, but a great deal 
of it is in the form of hygroscopic water; that is, water held in 
the pores of the rock by capillary attraction. 
An English geologist, H. B. Woodward, makes the statement 
that the quantity of water held in the chalk of England by 
capillary attraction is tremendous. One square mile of dry 
upper chalk, one yard in thickness, contains ordinarily nearly 
3,500,000 gallons of water, and when saturated holds 200,000,000 
gallons. Recent experimental work by Van A. Mills ° indicates 
that, in saturated strata, capillarity retards fluid movements, 80 
that water so held might not flow readily. 
* Econ. Geol. 15 (1920) 420. 
