The Audubon Societies 121 



Above 50°, it is growing cold, and we are also getting very far away from the 

 hot equator, so let us put down from 50° to 60°, "cold," and from 60° to the 

 North Pole, "very cold," describing this region as arctic, or boreal, in climate. 

 But we must not get the idea that all the hot and cold places on the earth are 

 either in the tropics or about the poles, for that is not true. We shall understand 

 this a little better if we picture differences in altitude and depth, that is the 

 height and depth of the earth's surface above and below the level of the sea. 

 Now the higher any part of the earth is above the sea-level in the atmos- 

 phere, or below it in the water, the colder it will be. Let us fix in our minds 

 the highest mountain-peaks in the United States, where the climate is 

 usually temperate or medium, and discover, if possible, how far north one 

 would have to travel to find a climate as cold as that which encircles these 

 lofty points.* 



When we stop to think of this matter, we know that in traveling from the 

 base of a mountain far up to its summit, we go from a warm, or moderately 

 warm, temperature to one much colder, just as truly as in going from the 

 equator toward either pole. 



In one case, we reach the cold region by going up as far as the land will 

 carry us above the level of the sea; in the other, we get as far away from the 

 hot part of the earth's surface as we can by going to the cold part, north or 

 south. 



If we look at the clay map now, and think about ivhere it is cold and where it 

 is warm, we will see that all the cold places cannot be around the pole, because 

 there are so many very high mountain peaks, as far south even, as New Mexico, 

 where it must also be cold. Just how to make our map show us where to look 

 for heat and cold is rather more difficult than to make it show where there is 

 land and water; but by sprinkling talcum powder over the clay, we can show 

 the coldest places, not only those that are high above the level of the sea, but 

 also those that are far from the equator. 



The reasons why it is hot or cold, high or low, or why there is land or water 

 at any one place, need not concern us here, but they make a long and interesting 

 story. 



The birds cannot think about these things, neither can the trees nor the 

 grass and plants; but they can all respond to heat and cold, and the birds can 

 see high and low places as well as the difference between land and water, 

 while plants and trees can go down below the earth, as well as up into the air 

 above it. Each tiny seed that is dropped into the soil, makes a wonderful 

 journey from the dark depths through which our eyes cannot see up into the 

 air and sunshine, just as truly as the bird, which travels from the hot equator 

 to the far cold north, or the mountain-climber, who leaves the grassy plains 



*See article on page 97 of this issue in wliich it is stated that in climbing up three miles in 

 altitude on Mt. Orizaba (Mexico), as great changes in vegetation and animal life are found as there 

 would be in going north three thousand miles in latitude from the base of this lofty elevation in the 

 tropics. 



