The Stratosphere is the layer of the Earth’s atmosphere which lies beyond the troposphere. It extends up to an altitude of 50 kilometres from the earth’s surface. This layer is almost free from clouds and associated weather phenomenon. It therefore makes conditions most ideal for flying aeroplanes.
Heifer – a cow that has not borne a calf, or has borne only one calf. In North America, a typical farm has about 100 milk cows and as many young female stock called heifers. The heifers are raised as replacement cows.