PHYSICAL AND METEOROLOGICAL RESEARCHES. 



207 



heavy rains revived tbe meadows and permitted the culture of a mid- 

 dling harvest. Hay was scarce. The temperature was very favorable 

 during the period of growth but the rainfall was deficient. The long- 

 drought was followed by a period of rain, storms, and cyclones, which 

 lasted until the end of autumn. These abundant rains retarded the 

 autumn sowing and seriously affected the vintage which had promised 

 so magnificently. Wine was plenty, but of poor quality. The autumn 

 temperature was very cold and considerably lower than normal. Win- 

 ter and spring until May were warm and dry, tbe summer almost 

 normal, while autumn was cold and rainy. Comparing the annual 

 temperatures for the last 12 years, it is seen that the years 1887 to 

 1891 were very cold and 1893 was very warm. Siuce then the curve 

 has declined. The relation which seems to exist between the tempera- 

 ture and the sun spots has already been pointed out. 



TEMPERATURE AT AND BELOW THE SURFACE OF THE SOIL 

 COVERED WITH GRASS. 



The temperature of the interior of the soil plays an important part 

 in the phenomena of plant growth. It affects a large number of food 

 plants which are produced under the surface as well as the roots of the 

 trees, which develop at various depths. One of the first duties of the 

 cliniatological station of Juvisy was the construction of thermometers, 

 registering instruments, etc., to be placed at various depths under the 

 surface of the soil to register the variations in temperature. The tem- 

 perature was recorded by an apparatus one meter above the soil, which 

 could be read and compared constantly. Five thermometers composed 

 of metallic cylinders filled with spirits of wine were placed at depths 

 of 0.05, 0.10, 0.25, 0.50, and 1 meter, to constantly register the tempera- 

 ture. The comparison of daily curves gives results which are curious 

 as well as important. Thus it can be seen that the amplitude of the 

 curve varies with the depth, being very large at 0.05 and nothing at 1 

 meter. The following table shows the monthly average temperature 

 observed at the surface of the soil and at different depths in 1896: 



Average temperature of soil and air at Juvisy during 1896. 



