Now, the distance that a windbreak will protect a field has been studied out and measured and demonstrated by a great number of men.  Mr. McGee, at Indian Head, gave a great deal of thought and study to the windbreak proposition and measured the distances that the shelter-belt would shelter the crops, and he came to the conclusion that for every foot in height there would be an absolute protection for a rod in distance, and outside of that actual protection there would be a long distance that would be partially protected.  The same study was made by a gentleman in Iowa—­I can’t call his name just now—­and he came to practically the same conclusion as to the distance that the protection reached in proportion to the height of shelter-belt.

[Illustration:  Mountain Ash windbreak at Devil’s Lake, N.D.]

A Member:  I want a shelter mostly for apple trees.  Would it be five or six years before I receive any benefit, or seven or eight years?

Mr. Maher:  Plant your protection when you plant your apple trees, and you will have your protection sooner than you have your apples.  If you are going to do that, don’t put the shelter too close to the apple trees, which is a very common fault.

A Member:  How much distance would you allow for the roots?

[Illustration:  White Willow windbreak at Devil’s Lake, N.D.]

Mr. Maher:  I should say not less than 100 feet, anyway.

Mr. Moyer:  I live in southwestern Minnesota, about thirty miles from the South Dakota line, and I think it is a mistake to recommend the white spruce for planting out there.  The white spruce naturally grows towards the North Pole, it extends even up to the Arctic Circle.  Twenty-four years ago I purchased a dozen white spruce from Robert Douglas, who was then alive, and planted them northwest of my house.  About five years ago they began to fail, and now only two or three are alive, and they are covered with dead branches.  I feel sure that the white spruce have been injured by the hot winds that come across the prairies from the southwest.  I don’t think they can stand it.  There is a variety of white spruce that grows in the Black Hills, which I think will be decided to be a different species when botanists come to study it, that will stand our prairies.  Another tree that we like is the Colorado blue spruce; it is hardy and grows excellently.  About twenty-three years ago, when Professor Verner was at the head of the Forestry Department at Washington he sent me 8,000 evergreens, and I set them out.  They were bull pine and the Scotch pine and Austrian pine.  I was over to look at them the other day.  The Scotch pine, which have been set now twenty-three years, are over thirty feet high, the Austrian pine about two-thirds as high, and the bull pine, Ponderosa, is about as high as the Austrian pine.  He told me to set these trees about two feet apart each way.  I thought that too thick, so I set them in rows six