B= 
T-3 have also included dredging operations to continue the areal study of 
the gravels. The gravels of Station Alpha have been the subject of a 
published study. The results of a study on the molluscs dredged in these 
operations have also been published. 
The Arctic Ocean floor has been observed directly on bottom 
photographs for the first time. Camera stations were made from Station 
Alpha and Station Charlie. Photographs were taken both in the relatively 
deep water of the Alpha Rise and in the relatively shallow water of the 
Chukchi Rise. The Ewing underwater camera functioned well and needed 
no special adaptation to the Arctic Ocean. The only care needed was in 
the summer when a layer of fresh water was on the hydro hole. Then, as a 
piece of gear was lowered, it might pick up some fresh water which would 
freeze as soon as it hit the colder saline water below. The best solution 
was to keep the instrument warm in a building until just before it was 
lowered. This ice layer was a nuisance to Nansen bottles and nets as well 
as to the camera. Only a few colored pictures were taken. The color emulsion 
is very sensitive to moisture and most of the film was washed out. It is 
necessary to have the camera case very dry for color work. 
Underwater sound was investigated at all three stations and received 
particular emphasis at Station Charlie and on T=3.6 At Station Charlie many 
recordines of shots by the Navy at T-3 were recorded-using hydrophones and 
an oscillographic camera. The records have yielded to interpretation as 
normal mode propagation and the results will be published soon. The Arctic 
Ocean proved to be an efficient wave guide for low-frequency sound. The 
sound energy is trapped along a surface axis and charges of several pounds 
are probably detectable throughout the Arctic Ocean. Calculations of 
frequency versus velocity were made for waves in a velocity structure which 
