148 Part II. Chapter 2. 
Character of rainfall. It is a matter of interest to ascertain whether the 
rainfall at any particular place is due largely to small rains, or to great ones. 
If the former is the case, it will generally be favorable to agricultural operations 
and not damaging to crops. Four types may be distinguished by a study of 
the meteorologic maps and records. The first type is that which is found on 
the lower lakes and which has its extreme at Oswego in New York. Its 
especial characteristic is the relatively large number of days on which small 
rains fell. This number of days is often greater than those on which no rain 
ell. This is particularly the case with these rains in winter, but it may extend 
in some cases through the year, and at Oswego it is found that this maximum 
appears clearly in the annual rainfall curve. The second type is best illustrated 
in the extreme northwest, but it is more clearly seen over our northern lati- 
tudes generally, except on the great plains, where the rainfall gradually passes 
into the fourth type. In the northeast, there is a combination of type two 
with type one, the traces of the latter decreasing as the distance from the 
lower lakes is increased. Type one is that of smallest rainfall, type two of 
small rainfalls. The third type belongs to the southeast and is best marked 
at New Orleans, La. It is marked by a greater number of medium rainfalls, 
due to the fact that the rains in our southern latitudes are largely local rains- 
thunderstorms, showers, etc. The rain of our northern latitudes comes usually 
in connection with general storms; the rain of the southern latitudes with 
local storms. Medium rains of short duration are, therefore, more frequent in 
the southern states. The fourth type is that of little rain. It is found in the 
drier regions of the United States, and is best marked at Yuma, Arizona. 
There is little rain of any sort and this usually comes with small showers, but 
cloudbursts occasionally occur. The rains of this type are generally local. 
Clouds. The average cloudiness is about 55 per cent. over the country 
in January, with over 70 per cent. in the north Pacific states, 25 to 35 per cent. 
in the south Pacific states, 40 per cent. in the south plateau region, 45 per cent. 
in the Missouri Valley, and 70 per cent. in the lower lakes. In July, there is 
ä diminished cloudiness, about 45 per cent., with 40 to 50 per cent. on the 
Pacific coast, 15 to 25 per cent. in the interior near the Pacific, and 45 t0 
5o per cent. on the Atlantic coast. The diurnal range of clouds over the 
whole country shows a minimum about midnight and a maximum at 2 to 3 p-M- 
3. Mexico. 
Zones. — Although Mexico is intersected by the Tropic of Cancer, yet itS 
geographic position gives it a great diversity of climate determined far more 
by altitude than its distance from the North Pole or the Equator. The heat 
of the torrid zone is experienced on the seacoast and the low, marshy tracts 
bordering on the Gulf of Mexico, and in the enclosed valleys 3,000 feet above 
sea level. Thus the City of Mexico in latitude 19° zı' N, at ah elevation of 
7,340 feet enjoys a much more general climate than New York, or Chicag®. 
The night breezes temper the heat of the day and the rains- which begin 
