Horse Latitudes

Image from atp forum

The horse latitudes are the regions above and below where the trade winds blow. Located around 30 degrees north and south, these areas are characterized by calm skies and minimal precipitation. 

In these high pressure zones, the easterly trade winds diverge from the prevailing westerlies of the temperate zones. 

Legend has it that the name horse latitudes was born when sailing ships bound for North America carried horses as cargo to the New World. Becalmed in these areas, sailors would throw the poor animals overboard. This conserved drinking water until the ship could get moving once more. 

Sitting becalmed and waiting for a wind was a terrible situation for a sailing ship. This is well described in the weird tale "The Rime of the Ancient Mariner," by the British Romantic poet Samuel Taylor Coleridge:

Day after day, day after day,	115
We stuck, nor breath nor motion;
As idle as a painted ship
Upon a painted ocean.