FRENCH INVESTIGATIONS. 29 



questions of forest influence on climate, and to this end instructed the 

 school of forestry at Nancy to undertake the necessary studies. In 

 April, 1886, observations were commenced by Prof. Mathieu, of Nancy, 

 with the view of determining the inttnence which a wooded or unwooded 

 country has upon the moisture received from the air. Three stations 

 were selected ; they were described by Dr. Hough in his report for 

 1877,* page 202. The most interesting feature about them is the forest 

 rain gauge at Cinq-Franchees. It was made to cover exactly the sur- 

 face covered by the tree-top and was jilaced with the tree in the center, 

 careful arrangements having been made to direct into the gauge all 

 water Avhich ran down the tree. In 1870 a fourth station was added, 

 that of the agricultural station of the school. The altitude of this sta- 

 tion is 712 feet, somewhat less than the others. 



In February, 1874, forest observations were undertaken by MM. 

 Fautrat and Sartiaux, and contiiuied by the first. The stations were 

 in the department of Oise, a few miles north of Paris. This is a rolling 

 territory of no great elevations or irregularities, and the southern part, 

 containing the better-known forest of Compiegne, is well wooded and 

 somewhat swampy. One pair of stations was in the state forest of 

 Halatte, about a cluster of oaks and hornbeams of twenty or thirty 

 years. The forest itself is large, containing about twelve thousand 

 acres. M. Fautrat had the happy idea of trying some observations 

 above the forest. His stations were therefore duplicated, one being 

 below at the height of 4J feet (1.37 m.), the other above the trees 

 about 20 feet (6.09 m.), and 46 feet (14.02 m.) above the ground. The 

 forest station was reproduced 1,000 feet (304.8 m.) away in the open 

 fields. Each station had thermometers, psychrometers, rain gauges, 

 and evaporometer. Under the trees tiie number of rain gauges wiis in- 

 creased to six, distrilnited in such a Avay as to give a good indi(;ation 

 of the amount of rain passing through the foliage. The stations were 

 on a soil of fine sand, cemented by clay, and were at an elevation of 354 

 feet (107.9 m.) (base) above the sea and 400 feet (121.9 m.) taken above 

 the trees. About 5 miles (8.04674 kil.) away was a second pair of double 

 stations; they were in and near the state forest of Ermononville. The 

 trees were twenty-five year pines, about 40 feet (12.19 m.) high. The 

 stations at Halatte were duplicated here, including the elevation of the 

 station above the trees. This brought the higher instruments to within 

 a very short distance of the foliage — 5 or 6 feet. The soil here was a 

 coarse white sand, and the open-field station was on a sau<ly plain. 

 The elevations above the sea were 302 (92.05 ni.) and 341 (103.9 m.) feet. 

 There were six ordinary gauges under the trees and an additional large 

 one, over 5 feet (1.52 m.) in diameter, which surj'ouuded the trunk of a 

 large pine tree. The printed observations (in the Coniptes roidm) are 

 somewhat fragmentary and extend over about four years. There has 



•Keport on Forestry, vol. i, Uuited States Departmout of Agriculture. 



