Essentials of fruit culture; Varieties of apples, apple culture, apple pests and injuries, apple harvesting, storing and marketing; cherries, apricots and quinces

Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...OF FROST INJURIES 8. More or less moisture always exists in the atmosphere in the form of an invisible vapor. When this invisible vapor is condensed by a falling temperature, clouds, or fogs, are formed; if the moisture in the clouds is further condensed at a temperature above the freezing point rain is formed; and if condensed at a temperature at or below the freezing point snow is formed. If the moisture of the atmosphere that is in immediate contact with the surface of the earth is condensed at temperatures above the freezing point, dew is formed, and if this moisture is condensed at or below a freezing temperature frost is formed. Frost is, therefore, the moisture of the air condensed at or below 32 F. on the surface of the earth or on plants or other objects. 9. Prediction of Frost.--The conditions under which damaging frosts may occur are so numerous and varied that it is very difficult to tell when frosts will occur and when they will not. However, frost may be expected during the night if, at nightfall, the dew point is 42 F. or less. The dew point is the temperature of the air at which dew is deposited. And when the dew point falls to 32 F. or lower, frost will occur. The dew point is determined by means of wetbulb and dry-bulb thermometers and a specially prepared table known as a dew-point table. The most accurate kind of an instrument for the determination of the dew point is shown in Fig. 4 (a), and is known as a sling psychrometer. This instrument consists of a wetbulb and a dry-bulb thermometer, securely fastened to a support, which, in turn, is attached to a handle in such a way that the thermometers and their support may be whirled on one end of the handle. A case in which the sling psychrometer may be kept while not in use is shown in (b)....