56 BURTON EDWARD LIVINGSTON 



The Piche-Cantoni Atmometer (Fig. 2) 



This instrument 7 is a modification of that of Piche, the reser- 

 voir of water being here placed below and the paper disk above. 

 Practically all the essential details of operation are the same as 

 with the Piche, excepting that the spasmodic water move- 

 ment (coincident with having the reservoir above) is here avoided, 

 and that the evaporating surface may be placed at a considerable 

 distance from the reservoir, in more satisfactory relation to plant 

 foliage, etc. Distilled water should be used.' 



The Pickering A tmometer 



In the Pickering instrument 8 a rectangular piece of absorbent 

 paper or cloth is held vertically by a suitable frame, and evapo- 

 ration proceeds from both sides. Water is supplied by means of a 

 tongue of the absorbent material reaching from the lower edge 

 of the rectangle into a covered reservoir of distilled water below. 



The Paper Cylinder (Fig. 3) 



The atmometer with paper cylinder 9 is a modification of the 

 Piche-Cantoni form, with the paper disk replaced by a hollow 

 cylinder of absorbent paper, closed at the upper end, where it is 

 applied against the supply tube. Distilled water is employed. 

 It has all the advantages of the Piche-Cantoni instrument and the 

 additional one of exposing a cylindrical evaporating surface. Its 

 main weakness as a cylindrical form lies in the fact that air leak- 

 age sometimes occurs at the junction of supply tube and paper 

 cylinder, but a better form of mounting should obviate this dif- 

 ficulty. It is notable that the Livingston paper cylinders evap- 

 orate little or not at all from the interior surface, while the three 

 paper forms above mentioned allow water loss from both sur- 

 faces. 



7 Cantoni, G., Sulle condizioni di forma e di esposizione piu opportune per 

 gli evaporimetri. Rend. R. 1st. Lomb. II. 12:941-946, 1879. See also the 

 writer's article on paper atmometers cited above. 



8 Pickering, S. U., and Bedford, Duke of, A new form of evaporimeter. Wo- 

 burn Exp. Fruit Farm Report 1897: 168-174, 1897. 



9 Livingston, B. E., Paper atmometers for studies in evaporation and plant 

 transpiration. Plant World 14: 281-289, 1911. 



