REPORT OF CRANBERRY SUBSTATION FOR 1914. 93 



extent, it is a factor that should be considered in making frost predictions 

 in connection with the growing of cranberries and possibly of other crops 

 also. It should be noted, however, that the results here discussed are 

 at variance with those obtained by Prof. H. J. Cox on the Wisconsin 

 marshes ("Frost and Temperature Conditions in the Cranberry Marshes 

 of Wisconsin," by Henry J. Cox, 1910, Bulletin T. of the Weather Bureau, 

 United States Department of Agriculture, page 61). Professor Cox shows 

 that in comparative studies he obtained the lower temperature readings 

 over the soil containing the greater amount of moisture and states that 

 the increased moisture was "solely responsible for the relative low tem- 

 oerature readings, on account of the heat lost in the evaporation of the 

 surface." The greater specific heat of water, as compared with dry earth, 

 should not, however, be lost sight of in considering this matter. 



Frost Protection. 

 Experiments with cloth, such as is used in growing tobacco under shade, 

 were carried out in September, to see if it could be used satisfactorily in 

 protecting bogs from frost. In these tests a strip of new cloth was sup- 

 ported by wires held 3 feet above the ground by stakes, about 9 square 

 rods of rather dry, grassy low land being covered in this way, the cloth 

 being brought down to the ground to shut in the covered area on all sides. 

 The cloth was spread out for the tests after sundown on cold nights, and 

 was always removed soon after sunrise, so that the ground might be 

 normally exposed to the heat of the sun during the day. Considering 

 the very coarse weave of the cloth, it retarded the rise of heat from the 

 ground to a surprising extent, evidently because the heavy dew that ac- 

 cumulated on it closed its openings considerably. A Green minimum 

 thermometer was placed at the center of the covered area, with its bulb 

 5 inches above the grass-covered ground, and a similar thermometer 

 at the same elevation, located over grass about 20 feet outside of the 

 cloth, was used for comparison. No frost formed on the covered ground 

 during the tests even when the surrounding low land was white with 

 it, and the thermometers showed that the cloth gave an advantage of 

 more than 4i/o° in temperature, as shown by the readings in the following 

 table : — 



Table 1. — Effect of Cloth Cover on Temperature. 



1 This reading was unusually high, as compared with that over "Area 1," as was shown by 

 numerous readings of these thermometers observed later, but not recorded. 



