260 The Principles of Fruit-growing 



Making currents of air. 



Since frosts occur on still nights, it is sometimes pos- 

 sible to prevent them by keeping the air in motion, thereby 

 mixing the air and preventing any part of it from lying 

 on the plant until it shall have become frost-cold by loss 

 of radiated heat. In small areas, as in choice gardens, it 

 is often feasible to undertake such means. It has been 

 suggested that windmills be set in motion by electric or 

 other power, or that mechanical fans be installed. These 

 methods appear not to have been applied commercially. 



Adding vapor of water to the air; flooding. 



An abundance of watery vapor in the air tends to 

 check the radiation of the earth's heat, and the addition 

 of water-vapor has an influence in raising the dew-point. 



The means of adding vapor to the atmosphere are 

 several: Spraying, flooding and irrigating, mulching and 

 tilling. The machinery used in spraying for insects and 

 fungi may be used for this purpose. Elaborate stand- 

 pipe devices, connecting with underground pipes, have 

 been used to facilitate the spraying of orchards. How 

 much relief may be found from these practices is yet 

 doubtful. The soaking of plantations to protect from 

 frost is practicable in places where vineyards are arranged 

 to be flooded for the destruction of phylloxera. Irrigating 

 systems may also be used to add moisture to the soil, and 

 therefore to the air, when frost is anticipated. 



"Cranberry bogs, being always lower than the surround- 

 ing land, are peculiarly liable to damage by frost, serious 

 loss frequently occurring when an ordinary farmer would 

 not dream of danger, and a good supply of water is the 

 only preventive that has been found efficient. The time 

 of starting growth in the spring may be controlled by the 



