'6o4 



Jountal of Agriculture. 



[lo Sept., 1910. 



traction spray pumps it would be possible to spray against frost, even on 



a fairlv large scale. 



Prediction of Frost. 

 The direct measures referred to above lead us naturallv to the question 



■of frost prediction. 



If one can know the previous even- 

 ing, with anything like accuracy, what 

 risk there is of a frost the following 

 uKirning, so that preparations may be 

 made to combat it, one of the prin- 

 cipal difficulties is removed. To be 

 obliged to watch the thermometer 

 e\'ery night and, more especially, dur- 

 ing the early hours of the morning, 

 over a period of several weeks is, to 

 say the least, irksome. 



Frost prediction is not only pos- 

 silile, but a comparatively simple mat- 

 ter. The moisture of the air having 

 so important a bearing on the question 

 (see page 598) the determination of 

 the dew point gives very reliable in- 

 formation as to the danger or other- 

 wise of frost. 



Instructions as to the determination 

 of dew point by means of the wet and 

 drv bulb thermometer and dew point 

 tables are given in the article l)y Mr. 



WET AND DRY BULB THERMOMETER. 



■.Should the dew point, according 

 to observations taken about sun- 

 set, be in the neighbourhood of 

 32 deg. F. there will almost 

 certainly V)e a frost unless a 

 wind springs up, or the sky be- 

 comes cloudy. 



In order to do away with the 

 necessary calculations a simple 

 table was devised some years 

 ago by a Viennese instrument 

 maker, Mr. H. Kappeler, 

 which so simplifies matters that 

 a slight modification of it is 

 here reproduced, with the Cen- 

 tigrade degrees converted to the 

 Fahrenheit scale. The read- 

 ings of the wet and dry bulb 

 thermometer, of which there are 

 many makes on the market, are 

 taken. These are referred to 

 in the chart. If the intersection 

 of the thin line from the wet 

 F)ulb reading, with the thicker 

 one from the drv bulb reading. 



(;. H. Adcock (Vol. TI.. p. 343). 



DIAGRAM FOR PREDICTION OF FROST. 



