In order to work with gradients and straight lines successfully, a good understanding of coordinates and linear graphs is needed. The gradient of a line is calculated by dividing the difference in the ...

Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.

THE accompanying diagram (Fig. 1) suggests a striking example of wave motion in the vertical temperature gradient at St. Hubert Airport, near Montreal, during a large inversion of early morning of Oct ...