224 horticulturist's rule-book. 



between the readings of the dry and wet bulb is entered in 

 the horizontal line at the top, from 1° to 13°. To find the 

 temperature of dew-point at any observation, find in left-hand 

 column the temperature of dry -bulb, then follow the horizontal 

 line opposite that figure till you reach the perpendicular col- 

 umn under the difference between dry and wet bulb readings, 

 and the figures at the meeting of these two columns will give 

 the temperature of dew-point. For example, suppose the dry- 

 bulb stands at 65° and wet-bulb at 55°, the difference is 10°. 

 Pass across the page in the line of 65° till you intersect the 

 vertical column under 10° and you read 47°, which is dew-point 

 .under these conditions. If the dew-point is 10° or more above 

 frost-point (32° Fahrenheit), there is no danger of killing 

 frost ; but if the dew-poiut is less than 10° above 32°, danger 

 may be apprehended. If a line is drawn from the intersection 

 of 43° — 1° and 67° — 13°,. of the table, this may be called the 

 danger line, and all dew-point temperatures below this line 

 indicate danger of frost, and are printed in italics. This mar- 

 gin of 10° is taken because the temperature on a still night 

 will sink a few degrees below the first dew-point, -and the 

 temperature of the air at 5 feet above the ground is several 

 degrees above that at ground level. For these reasons com- 

 bined a margin of 10° may be- safely assumed as the limit of 

 safety. 



To Protect Plants from Light Frosts. — 1. Make a snnidge 

 in the garden or vineyard at night when the frost is expected. 

 Rubbish or litter and tar make the best smudge. 2. Syringe 

 the plants thoroughly at night-fall. 



" If the farmer is forewarned of the approach of a still frost, 

 he may do something to avert the calamity. The conservative 

 influence of watery vapor is the most hopeful means of pro- 

 tection, and sometimes trivial causes of this class will produce 

 surprising results. The old plan of ' a tub of water under the 

 fruit tree, and a rope reaching from the tub into the branches,' 

 may serve a useful purpose. The evaporation from the water 

 in the tub and of the water carried up by capillary action in 

 the rope may spread th^ protecting folds of the water blanket 



