118 EXPERIMENT STATION EECOED. [Vol. 41 



results are said to bo obtained with the evaporators than with sulphuring, 

 although the initial cost of an evaporator is much greater. It is pointed 

 out, however, that the initial cost of an evaporator is only a fraction of the 

 loss during one rainy season such as that of 1918. 



A short discussion is given of the theory of evaporation and general prin- 

 ciples and defects of some present evaporators, followed by detailed de.scrip- 

 tions with specifications of the Oregon tunnel evaporator, an air-blast evap- 

 orator for wooden trays, and the small Young stack evaporator. General de- 

 scriptions are given of the kiln evaporator, Watsonville stack evaporator, and 

 the Anderson tunnel evaporator. 



Attention is called to the necessity in designing an evaporator of making 

 provision for sufficient heat production and radiating surface, good air circu- 

 lation, and control of temperature. For the small dry-yard, the Young type 

 of small stack evaporator is recommended, and for the average-size yard, 

 the Oregon tunnel evaporator. Where wooden trays are to be used the air- 

 blast evaporator is considered best. 



Scientific methods in the production, classification, and manufacture of 

 rubber, G. Van Pelt, {Inst. Colon. Marseille, Bui. Caoutchoucs, No. 1, {1919), 

 pp. 51). — This bulletin discusses the principal operations connected with the 

 exploitation of rubber from the production to the manufacturer! objects, with 

 a view to introducing a more scientific control of the various processes. As 

 a means to this end, the author recommends the establishment of laboratories 

 on the plantations, the collaboration of the scientific staff of the plantation 

 with the special laboratories, both nonofficial and official, in the producing 

 countries, the establishment of scientific standards for estimating the value 

 of rubber, the creation of a scientific organization for the study of questions 

 applying to the rubber industry, and the collaboration of this organization 

 with the technical service of the rubber factories. 



METEOEOLOGY. 



Relation between vegetative and frostless periods, J., B. Kincer {TJ. S. Mo. 

 Weather Rev., Ifi {1910), No: 2, pp. 106-110, pis. S, fic/s. 5).— The relation be- 

 tween the frostless period and the length of the period during which the mean 

 daily temperature is 43° F. or above is discussed on the basis of a series of 

 eight charts showing (1) the average dates in spring when the daily mean 

 temperature rises to 43°, (2) the dates in autumn when it falls below that 

 value, (3) the average number of days when the mean daily temperature is 43° 

 or higher in different sections of the country, (4) the normal mean daily tem- 

 perature on the average date of the last killing frost in spring for all regular 

 Weather Bureau stations in the United States, (5) similar data for fall frosts, 

 (6) and (7) the average number of days in spring and fall, respectively, by 

 which the potential growing season is shortened by frost, and (8) the total 

 number of days that the average frostless season is shorter than the vegetative 

 period. 



It is shown that the advent of the vegetative period in the average year 

 ranges from February 1 in the northern part of the Gulf States to May 1 in 

 extreme upper Michigan and northern New England, and that this period comes 

 to an end, on the average, about the middle of October in the extreme northern 

 districts, but continues till the end of the year in the South. The length of 

 the period ranges from less than 180 days in the extreme north and in the 

 central and northern i»ortions of the Rocky Mountain region, to 365 days in the 

 South Atlantic and Gulf districts, and also in the central and southern Pacific 

 coast sections. 



