THE FOREST AND SPRINGS 



367 



really reliable data are those obtained by means of the simple and reliable depositary 

 invented by Mathieu in 1867, which has been retained at the Research Station of Nancy, 

 during 32 years of observations. Here is the description of it, taken from the inventor 

 himself: !»' 



"La Station des Cinq-Tranchees, situated about 5 miles to the west of the town of 

 Nancy, at a height of 1,247 feet, is situated in the midst of a large wooded plateau, 

 'La Haye,' which the limestone strata form of the lower oolith. Two rain-gauges are 

 placed there; one in the middle of the wood, under a polewood of beeches and horn- 

 beams, moderately compact, of about 40 years of age in 1866. The other, at a short 

 distance from the preceding, is in the middle of an open space of about 5 acres, adjoining 

 the ' Maison Forestiere des Cinq-Tranchees.' 



"The quantity of rain water which a gauge receives, when placed in a forest, varies 

 with the position of the instrument in dense foliage or in openings. The forest rain- 

 gauge is especially constructed to avoid this source of possible mismeasurement; it is 

 provided with a receptacle of large dimensions, of which the circular surface is exactly 

 equal to the projection of the top of one of the poles of the clump.^" The stem of one 

 of these passes through the center, and is surrounded by a kind of collar; thanks to this 

 arrangement, the water which runs down the trunk can be collected, be it the result of 

 prolonged rainfall, or of a dense mist, or the effect of a thaw in producing the melting 

 of snow, or of hoar frost on the branches." 



These observations began in 1867 and were continued until 1898 when an accident 

 happening to one of the instruments prevented them from being carried on longer. 

 They embrace, however, a period of 32 years. 



The following table gives a resume of the results obtained: ^^ 



SUMMARY OF MONTHLY AVERAGES OF RAINFALL OUTSIDE AND 

 INSIDE THE FOREST 



* The figures for the individual months have been omitted and the data rearranged. 



A comparison of the foregoing figures will show us that, for a certain number of 

 months, especially in winter, the rain-gauge placed imder cover collects the greatest 



19 "Meteorologie Comparee Agricole et Forestidre; rapport a M. le sous-secretaire 

 d'fitat, etc.," of 2.5 February, 1878, p. 4. In this report, pubhshed by the "Imprimeri, 

 National," Mathieu gives an account of the results of the first eleven years of observa- 

 tions. 



2" This pole was a young hornbeam of about 41 years of age at the beginning of the 

 experiments, of a regular shape and with well crested top. 



21 This table is borrowed from the work by M. de Bouville already quoted: "Observa- 

 tions de meteorologie . . . de la Station de Recherches de f ficole National des 

 Eaux et For^ts," Paris, 1901. 



