1912.] 



Night Frosts in Spring. 



93i 



bushels per acre (or, at 45 lb. per bushel, no less than about 

 15 tons), and is given by Potts as averaging 7 to 8 tons, the 

 white and pink varieties when tested having yielded 9 tons 

 1 cwt and 6 tons 16 cwt. respectively. McConnell gives the 

 produce as 3 to 8 tons per acre, and, as a rule, the weight 

 of crop obtained is probably less than that of potatoes 

 on similar soil. In Wilson's Farmer's Dictionary already 

 referred to, it is stated that, "In Alsace, Jerusalem arti- 

 chokes are always grown, without any rotation, and with 

 manure only every second year, upon the same land. At 

 Bechelbronn, upon somewhat shallow soil, they produce per 

 acre 10 tons of tubers and nj cwt. of dried stems; and in 

 many situations, upon land of medium quality, and without 

 any manure, they produce per acre about 500 bushels of 

 tubers. The leaves and stems are used on the Continent as 

 both green and dry fodder." According to the American 

 Farmer's Cyclop cedia of Agriculture (1904) the yield varies 

 from 275 to 1,000 bushels per acre. 



The various means by which fruit trees may be protected 

 against late spring frosts have from time to time been dealt 

 with in this Journal,* and it may at 

 Night- this season be useful to call attention to 



Frosts in some notes on the subject of night frosts 



Spring - . in spring prepared for issue by the 



Meteorological Office two or three years 

 ago. The notes have been embodied in a chapter on the 

 subject in Forecasting Weather, by the Director of the 

 Meteorological Office (Constable & Co., Ltd.). 



Causes of destructive Frosts in Spring. — Destructive frosts 

 in spring may arise from three separate causes : (1) the 

 occurrence of the ordinary type of cold, wintry weather which 

 is not uncommon in spring, there being a northerly, north- 

 easterly, or easterly wind, indicating a cold spell, probably 

 with snow. (2) Changeable April weather, which can be re- 

 ferred to the passage of barometric depressions : if the baro- 



* Previous notes on the subject have appeared in the Journal as follows : April, 

 1906, p. 57 ; June, 1906, p. 184 ; Sept. 1906, p. 375 5 April, 1907, p. 23 ; Oct. 

 1908, p. 521 ; March, 1910, p. 1024 ; Oct. 1910, p. 558. 



3 S 2 



