Rules, Notes and Recipes 
205 
are really rather interesting. He says that in digging an acre of ground 
the operator lifted 972 tons of soil in the course of 120 hours’ work, 
and the total energy expended on an acre of digging was 3210 tons. 
Skinner Irrigation System. — In regard to the well known 
Skinner Irrigation System the average cost is about $250 per acre, 
including the pumping plant and water supply. The equipment in the 
field will cost probably $125 per acre. From $100 to $150 an acre would 
cover about nine-tenths of the installations so far as the field equip- 
ment is concerned. The rest of the cost is included in the pumping 
plant, and the cost of this varies considerably with the conditions. It is 
usually figured that the capacity of the pumping plant may not neces- 
sarily need to be equal to the full capacity of the field installation. 
The Skinner System distributes water at the rate of an inch of rainfall 
in from nine to eleven hours. An inch of rainfall in two weeks is the 
average requirement of a crop; under conditions of drought Occasion- 
Results of Correct and Incorrect Pruning of Trees 
a, correct method after two years; 6, incorrect method 
ally a plant requires more water than this, but the average requirement 
is as above indicated. The selection of water from a well or from a 
stream is a matter to be determined by local conditions entirely. 
Theoretically, river water is preferable to well water. 
Tent Caterpillar. — The webs of this injurious caterpillar are 
common in nearly all parts during May. They are especially found in 
the Wild Cherries and in ill-kept orchards, but the “worms” will also 
eat the leaves of a large number of forest trees. One of the very best 
ways of combating this insect is by collecting and destroying the egg 
masses during the Winter or early Spring. (See illustration, page 191.) 
Tree Surgery. — Much greater care is taken of decaying or injured 
trees than formerly. Tree surgery has been brought to a high degree 
of perfection, and examples of clever work may be seen in many 
places. The first operation is the cleaning out and thorough removal 
of all decayed material, no matter how far the decay extends. The 
entire surface of the cavity is then disinfected and waterproofed. One firm 
has a patented device, known as the water-shed, which also excludes 
