or map gradient
and not the engineer's gradient. The latter is generally used, I
understand, to measure the gradients of roads, railways, etc.

To avoid confusion when Ski-ing, the gradient is usually named by the
angle of the slope.

The gradient of slopes is shown by the contour lines, the drop between
each being 30 metres or approximately 100 feet. The table on p. 92 was
got out by Commander Merriman, R.N., and has proved very useful to
me in setting tests as well as in judging whether slopes are
comparatively safe from avalanche or not.

A slope showing eight 30-metre contour lines in one centimetre works
out roughly at 27 deg., which is a steeper slope than most people care to
take straight, running over unknown country. Anything steeper than
this is apt to avalanche in certain conditions, though a 30 deg. slope
should usually be safe. (A 25 deg. slope may be dangerous under some
conditions.)

A comfortable slope is 5 contour lines in 1 centimetre, or a gradient
of 17 deg.. Taking English measurements as in Commander Merriman's scale,
16 contour lines in one inch on the map.

The beginner will probably content himself with slopes where 10
contour lines are shown in one inch, or a gradient of about 13 deg..

ROUGH TABLE OF GRADIENTS.

Assuming 30 metre contours to be equal to 100 feet contours
(actually this is 98.4 feet). Natural Scale 1: 50,000.

--------------------------------------------
Drop per inch | Average angle | Gradient
on map. | of slope. | 1 in.
--------------------------------------------
100' | 1 deg. 24' | 40.9
200' | 2 deg. 45' | 20.8
300' | 4 deg. 07' | 13.9
400' | 5 deg. 29' | 10.4
500' | 6 deg. 50' | 8.3
600' | 8 deg. 12' | 6.9
700' | 9 deg. 33' | 5.9
800' | 10 deg. 52' | 5.2
900' | 12 deg. 11' | 4.6
1,000' | 13 deg. 30' | 4.2
1,100' | 14 deg. 47' | 3.8
1,200' | 16 deg. 04' | 3.5
1,300' | 17 deg. 20' | 3.2
1,400' | 18 deg. 34' | 3.0
1,500' | 19 deg. 48' | 2.8
1,600' | 21 deg. 00' | 2.6
1,700' | 22 deg. 11' | 2.5
1,800' | 23 deg. 22' | 2.3
1,900' | 24 deg. 30' | 2.2
2,000' | 25