54 
HINTS TO TRAVELLERS, 
subtends an angle of 18°. This may be easily checked by spanning round 
the horizon; twenty spans make the circuit. It is at all times well 
to know the length of the different joints of the limbs. Suppose the 
nail-joint of the forefinger to be 1 inch, the next joint will be II inches, 
the next 2 inches, and from the knuckle to the wrist 4 inches; in this 
case the finger is bent, so that each joint may be measured separately, 
though, when held straight, the distance from the tip of the forefinger to 
the wrist would be only 7 inches. The span with thumb and forefinger 
would be 8 inches, and with the thumb and any of the other three 
9 inches, or equal to the length of the foot; from the wrist to the elbow 
would be 10 inches, and from elbow to forefinger 17 inches, and from 
collar-bone to forefinger 2 feet 8 inches; height to the middle of the 
kneecap 18 inches. From the elbow to the forefinger is usually called a 
cubit, but it is seldom strictly so, an English cubit being generally stated 
as 18 inches. In like manner the full stretch of the extended arms is 
called a fathom; but it is generally somewhat less. 
