1890.] On the Question of the Fixation of Free Nitrogen. 89 



Per cent, 

 nitrogen. 



In lupin sand, alone 0*0863 



In lupin sand, with bine lnpin ash 0*0826 



In lnpin sand, with yellow lupin ash .... 0*0888 



Mean 0*0859 



It may be stated that, in this country, lupins are only grown as an 

 agricultural crop, as food for sheep, on poor, sandy soils, on which 

 little or nothing else will grow. The sand obtained for the purposes of 

 the experiments was from land which had been reclaimed from a com- 

 mon in Suffolk, and on which no corn crop would grow; but on which, 

 when subsequently sown with blue lupins, they had grown as high as 

 the hurdles. It is stated, however, that lupins grow better on good 

 land, but that they are grown on sandy wastes because they will 

 thrive on them when no other crop will. 



The garden soil, in the condition as analysed, contained 10*12 per 

 cent, of moisture, and two determinations of nitrogen by soda-lime 

 gave 0*3902 and -0*3936, mean 0*3919, corresponding to 0*4360 per 

 cent, on the soil dried at 100° C. 



The pots used were made of glazed earthenware ; and were about 

 7 inches high, 6 inches in diameter at the top, and 5|r inches at the 

 bottom, inside. They had a hole half an inch in diameter at the 

 bottom for drainage, and another at the side near the bottom, into 

 which, outside, a glass tube bent upwards was fixed for aeration ; 

 the tube being lightly closed with cotton-wool to prevent insects getting 

 in. The pots rested on slips of thick sheet glass, placed in basins 

 of the same glazed earthenware as the pots. 



The mineral nutriment used was as follows : — For the peas, a mixture 

 of 6 parts of pea-straw-ash and 1 part of pea-corn-ash ; for the blue 

 lupins, a mixture of 3 parts of blue lupin-straw-ash and 1 part of blue 

 lupin-corn-ash ; for the yellow lupins, a mixture of 4 parts of yellow 

 lupin-straw-ash and 1 part of yellow lupin-corn-ash. In each case 

 the greater part of the mixed ash was suspended in distilled water, 

 and sulphuric acid added until there was a slight acid reaction ; the 

 rest of the ash was then added, and the whole evaporated to dryness 

 and re- ignited. The ash was then very slightly alkaline to litmus. 

 The so-prepared ashes were mixed at the rate of 0*5 per cent, with the 

 greater part of the sand put into the pots ; the remainder of the sand 

 at the top of the pot being wdthout ash. 



The drain hole at the bottom of each pot was loosely covered with 

 a piece of thick glass, 1 lb. of broken, washed, and dried flint was 

 then put in, next the sand with ash, and lastly the sand without ash. 

 The pots held from 7 to 9 lbs. of the yellow Flitwiek sand, from 6 to 

 7 lbs. of the lupin sand, and about 4| lbs. of the garden soil. 



