Vicki Clark, age 11, of Fredericton, ^I. B., Canada, for her question:

How come the deserts are so dry?

The world's mayor deserts lie within two wide belts, north and south of the equator. Here, as everywhere else, the regions are swept by prevailing winds. Also, as everywhere else, the winds gather moisture when they bloTr across vast oceans. Certain geographical features force the winds to shed their moisture as rainfall. For example, the prevailing vest winds from the Pacific drop rain when they are forced to rise by our western mountains.

IIhen our west winds get over these mountains, they have less moisture to shed. On the eastern side, large areas get less than their share of rainfall and we have stretches of arid desert and semi arid prairie. Similar geographical features create all the world's dry deserts. However, every spot on earth gets some rainfall, sometime. But a desert may sometimes get its quota for several years in a single deluge    which may be followed by years of drought.