548 
OCEANOGRAPHY: A. G. MAYER 
over these areas varies from a mere veneer to at least 2 feet. Along the 
outer vertical face of the reef on the opposite (north) side of this same 
cove many barren areas were found to be covered with a surface layer 
of spicule rock from 1 to 12 inches in thickness. This layer extends back 
into many subterranean caverns in the reef for a distance of several feet, 
and when added to the area of the reef face now covered with living 
alcyonaria constitutes an almost complete covering of spicule rock over 
the entire reef face for more than one-third of a mile from the head of 
the cove. 
While these observations have made it clear that on certain of the 
pacific reefs the alcyonaria are important coral forming agents their 
relative importance can be determined only after borings have been made 
through some reefs to determine whether or not the present conditions 
are transient or have been maintained over long periods during the up- 
building of the reefs. 
OBSERVATIONS UPON THE ALKALINITY OF THE SURFACE WATER 
OF THE TROPICAL PACIFIC 
By Alfred Goldsborough Mayer 
DEPARTMENT OF MARINE BIOLOGY. CARNEGIE INSTITUTION OF WASHINGTON 
Communicated, June 22, 1917 
On a voyage from San Francisco, CaHfornia, to Honolulu and thence to 
Pago Pago, Samoa; and also upon the return over the same route, we 
made daily observations of the hydrogen-ion concentration of the surface 
water, using for this purpose a set of thymolsulphonephthalein tubes 
standardized and prepared by Prof. J. F. McClendon, and kindly 
presented to us for this purpose. 
It was found that in the mid-Pacific, N.N.E. of Samoa, the surface 
water at or near the equator was cooler, and less alkaline than.5°-10° 
north or south of this region. This fact will appear upon inspection of 
the tables at the end of this paper. It seems that the water of the equa- 
tor at 24? 9 C. is so low in alkahnity as to be comparable in this respect 
with the water of only 15°C. about 300 miles off the mouth of San Fran- 
cisco Harbor, California. 
The low alkalinity of the water near the equator was usually although 
not invariably associated with a decided easterly set opposite in direction 
to the prevailing westerly surface drift of the tropical Pacific. 
This suggests that counter currents at the surface in the tropical 
Pacific may be regions wherein the cold bottom water is rising to the 
surface; and that this cold water has not yet had time to come into 
