METHOD OF ECOGRAPII BATTERIES 93 



and, in such case, the task of primary importance is to establish the physical 

 character of representative habitats. For these reasons, the first series of 

 thermographs established in 1903 was located with respect to altitude, the 

 instruments being placed at Manitou 2,000 m., Minnehaha, 2,600 m., and 

 Mount Garfield 3,800 m. In 1904, the stations established for the record of 

 temperature and humidity were situated with respect to habitats represent- 

 mg the four formations : gravel slide, half gravel slide, spruce forest, and 

 brook bank. 



The batteries are located and set up according to the directions already 

 given. A 2-meter quadrat with the battery as the middle is staked and 

 mapped. Within this, all readings of water-content, soil temperature, and 

 physiographic factors are made. Altitude, slope, exposure, and cover are 

 recorded when each battery is located, and a soil sample is taken for me- 

 chanical analysis. When the position of the batteries permits it, water-con- 

 tent readings should be made frequently, once or twice a week at least. In 

 addition, a complete series of samples should be taken daily for a period 

 sufficient to indicate the ordinary extremes of water-content. 



The ecograph battery of each habitat constitutes a standard to which the 

 results obtained by simple instruments may be referred with accuracy. It 

 not only does this, but it also serves as a basis for interpreting the readings 

 of simple instruments in distant habitats of the same character. In this way 

 a few batteries judiciously placed make possible the exact physical investiga- 

 tion of a large number of habitats, covering a considerable area. The only 

 limit, indeed, upon this method is that placed by time. The proportionate 

 use of batteries and of simple instruments must be largely determined by 

 the conditions which confront the investigator. It is obvious that, where 

 expense is not a decisive factor, the gain in time and in completeness of 

 results is enormously in favor of the battery. There is an additional value 

 in the automatic and continuous record which can not be overlooked. When 

 the use of instruments in the study of habitat and formation becomes uni- 

 versal, the importance of the ecograph will be immeasurably enhanced. It 

 will be possible to secure duplicate records of batteries located in the most 

 remote and diverse regions, from the equator to the poles, and comparative 

 phytogeography upon a scientific basis will for the first time be possible. 

 This opens an alluring vista of the future when ecologists the world over 

 will cooperate in such a way that the results obtained by ecograph batteries 

 anywhere on the globe will permit of exact comparison. 



