353 



a third of like doptli aiul 1 meter wide, into which a stairway descends 

 from the level of the j;r«mnd ontside. The i»assai;es are closed at the 

 top by tarred planks which are covered by a layer of sand. The boxes 

 of each row are separated from the i)assa^e wall and from each other 

 by si)aces 0.5 meter wide. Tlie rows of boxes between tlie two 

 ])assages are separated by a space 1.2 meters wide. These spaces are 

 tilled with soil. Thns each box is surronn<led on allfonr sides by earth. 

 The glass drainage tube which comes from the bottom of the front side 

 of the box is covered with an iron tube and itrojects througli the onter 

 soil and the brick wall of the passage into the passage itself. Here it 

 is joined by well-devised rubber and brass connections to a perpendicu- 

 lar glass tube, which may be called a sui>])ly tube, and thnmgli which 

 water can be poured for watering tlie soil from the bottom. A small 

 glass tube, projecting upward iuto this su})])ly tube from the bottom, 

 serves to remove the drainage water. It can be raised or lowered at will, 

 so as to have the upper end at the level at which the water table in the 

 box is to be maintained. If by reason of heavy rain the water of the 

 soil in the' box is increased so that the water table would rise above 

 this level, the excess runs oil" as drainage water. If on the other han<l 

 the siril gets dry and the level of the water table is lowered, it is easily 

 raised by either pouring water on the surface of the soil or by introduc- 

 ing it through the sni)ply tube. The height of the water table can be 

 seen at any tinu^ in the su])i>ly tube, which serves as a gauge. 



The boxes with the passages and stairway are surrounded by a strip 

 of lawn aiul inclosed by a wire fence, the wdiole iuclosure being some 

 18 meters long and 14 meters wide. 



The cost of each of the boxes was, for glass $15, setting in cement 

 and transport to the station $13.25, drainage and supply tubes and 

 setting $2.50, drain tiles $1, total $31.75; or for the 20 boxes, ^OSn. 

 To this must be added the cost of digging", setting the boxes, masonry, 

 inclosing, etc. — about $250. Other expenses will probably bring the 

 whole cost to not fai- from $1,000 foi- the conqdeted jdant for box exper* 

 iments. 



Close at hand are appliances for meteorological observations, includ- 

 ing rain gauge, barometer, psychrometers, and air and soil thernnmie- 

 ters. The soil thermometers are placed on the surface of the soil and at 

 depths of 0.02, 0.05, 0.15, 0.25, 0.50, and 1 meter. The underground 

 thermometers are inserted horizontally into the soil through a wall of a 

 ]>assage 1.5 meters deep, specially sunk into the ground for the purjiose. 

 The bulbs reach in to a Inuizontal dei»th of 0.5 meter, excei)t in the case 

 of the two lowest, which extend to lateral depths of 0.75 and 1.25 meters, 

 respectively. The scales reach outside, so that the tridaily readings can 

 be made with the greatest convenience. 



The station at Tharand, with whi(dj the one at Dresden is closely 

 affiliated, is engaged in the study of the action of bacteria in the 

 assimilation of the ^nitrogen of the air by plants. In the division of 



