DEEP-SEA EXPLORATION. 
377 
semicircle, when healed to starboad, the ship’s liead is thrown to leeward, or toward 
the lower side.* 
When heeled to port the shills head is thrown to leeward when on any course 
between southeast and northwest through north, and to windward when on any course 
to the southward of southeast and northwest. While building, the ship’s head pointed 
N. 29° 30’ W ; the ways were in latitude 39° 44' K., longitude 75° 33' W. 
The sextants and octants are of the ordinary type. One, the lunar sextant, has an 
attachment called the Tanner flexible staff, its purpose being to eliminate the nervous 
tremor of the observer or the effect of wind upon the instrument when observing with 
the artificial horizon. 
It is an ordinary wooden staff, 2 feet 6 inches in length, not unlike a walking stick, 
its upper end flattened on one side and pierced with a |-iuch hole, and a spiral spring 
of phospher bronze is inserted between the severed parts, 8 inches from the head of the 
staff, forming a flexible universal joint. 
A brass plate with screw thread and thumbscrew is let into the back of the sextant 
handle, and to mount the apparatus for use it is only necessary to connect staff and 
handle by means of the thumbscrew. 
I i 1 S' 8 4 » I 
Cut 72. — The Tanner flexible staff. 
A convenient position for observing is to sit on a camp stool, with elbows resting 
on the knees, and the staff planted firmly on the ground, at an angle that will afford 
the desired support and enable the observer to change the position of his instrument 
at will through the flexion of the joint. 
The staff should be made of light material, in order to interfere as little as possible 
with the handling and reading of the sextant. 
The taffrail logs, both the Walker and Bliss, are excellent instruments when 
properly cared for. The former is preferred when running steadily for a considerable 
time at high speed, while the latter is more convenient for short distances at varying 
speeds when the fractions of a mile are required, and the necessity for hauling in 
and putting out is of frequent occurrence, as in sounding and dredging. It is good 
practice for a vessel engaged in such work to keep one Walker log as a standard, 
using it for no other purpose, as the propellers of working logs are always liable to 
injury by coming in contact with the stern of the vessel or being struck by sharks or 
other fish. 
The Bassnett atmospheric sounder used in connection with the Tanner sounding 
machine for measuring depths within 100 fathoms, without changing the speed of the 
vessel, is, when used intelligently and properly cared for, a very useful and almost 
indispensable adjunct for coasting at night or in foggy weather. 
It operates on the principle of the compression of a column of air proportioned 
to the increase of pressure as it sinks beneath the surface. It is comjjosed of a glass 
* She has recently been supplied with compensating binnacles. 
