FIELD-GLASSES

A good binocular, preferably one which magnifies about six times, is a

great aid to the amateur. The field of the glass, its illumination, ease

of adjustment, and such points should be investigated before the

purchase is made. A well-made glass with good lenses is probably the

best in the long run, even though it be more expensive. Glasses should

be handled carefully. They should have a good carrying-case, and should

not be left lying in the sun nor exposed to the rain.

An Introduction to the Birds of Pennsylvania · 第 9 / 23 题