THE LOSS OF XITROGEiT. 105 



formed without any disturbance of the soil, and no veg- 

 etation is allowed to grow upon the area occupied by the 

 drain gauges themselves. Close to them is a rain 

 gauge of a similar size. We obtain by this arrangement 

 a knowledge of the rain-fall, and also of the amount of 

 rain wator which passes through the soil at different 

 depths. From time to time analyses have been made of 

 the water passing through the soil, and latterly the 

 whole of the nitric acid and chlorine which the water 

 contained has been determined. The results are in 

 course of publication. I do not propose, therefore, on 

 the present occasion, to do more than point out the im- 

 portant bearing these investigations have upon j)ractical 

 agriculture. 



The whole history of nitric acid, as regards its bearing 

 upon vegetation, is of quite recent date. The time is 

 within my own recollection when it was a question of 

 doubt whether the effect of nitrate of soda on vegetation 

 was due to the nitrogen or the soda. At the present 

 time it may be said that every farmer has an interest in 

 nitric acid, and that a correct knowledge of its properties 

 and action, with relation to our soil and croj^s, must be 

 the basis of all agricultural science. 



The amount' of nitrogen which passes through the 

 Eothamsted drain gauges every year since they were 

 established, if calculated upon an acre of land, would ex- 

 ceed forty pounds in weight. I have made an estimate 

 of the nitrogen contained in crops grown in the United 

 States, taking as my basis the average produce over the 

 whole country for ten years, and the amount removed 

 per acre would be very much less than this. Upon ordi- 

 nary arable land, therefore, which is not particularly fer- 

 tile, and has remained iincropped and at rest, more nitro- 

 gen passes each year through the soil than we should find 

 m an ordinary crop of grain, potatoes, or hay, grown m 

 the States. Let us add to this fact three others. (1.) 



