206 



BURTON E. LIVINGSTON 



porous porcelain, but any portion of the external surface may be 

 water-proofed if this is needed. For general use in auto-irriga- 

 tion it is perhaps best to water-proof the circular plate forming the 

 base of the cone and to treat the cylindrical neck, through which 

 connection is made with the supply reservoir, in the same w^ay. 

 The neck projects vertically above the conical part of the cup and 

 its upper end approaches or reaches the soil surface, or may pro- 

 ject above it. The best results are to be expected when the cir- 

 cular base rests directly on a rigid support, such as the bottom or 

 the sloping walls of the soil container. The diagram of figure 1 



Diagram showing arrangement of auto-irrigator with porous porcelain cone 

 I, cone; S, soil; B, mercury barostat; R, water reservoir. 



shows the general arrangement, and is self-explanatory. If the 

 soil container is large einough several cones should be placed side 

 by side. For deep containers it may.be desirable to place several 

 cones one above another, but they should all be rigidly supported 

 in some suitable way; for it is not desirable that the cone should 

 be lowered by shrinkage of the underlying soil. 



The new auto-irrigator cones have a circular base 7.5 cm. 

 (2f inches) in diameter, the total height is 9.8 cm. (3f inches) and 

 the cylindrical neck is 3.7 cm. 1t^ inches) high and 2.2 cm. (| 

 inches) in diameter. The wall is about 3 mm. thick. 



