ABSORPTIVE POWER OF TUKF. 113 



not show the total amounts of these substances which 

 the turf will absorb to the point of complete saturation, 

 but merely what it will take lip when simply mixed 

 with the solutions, and left in contact with them for a 

 few hours. If we add more of these solutions to the 

 turf-powder, the fluid exhibits an alkaline reaction, 

 which disappears again after one or more days ; and it 

 is only at the end of eight days, when the litre (1'76 

 pint) of turf has taken up 7*892 grammes (121*6 grs.) of 

 potash and 4*169 grammes (64*2 grs.) of ammonia, that 

 the alkaline reaction ' remains permanent. What we 

 shall hereafter designate as saturated turf contains 

 only i of the potash and -J- of the ammonia, which 

 would be absorbed by that substance to the point of 

 complete saturation. 



To represent different soils, containing various pro- 

 portions of nutritive substances, three mixtures were 

 made of saturated and ordinary turf-powder : 



1 mixture contained 1 vol. of saturated tnrf-powder, 



and 1 vol. of dry turf-powder, 

 3 " 1 ' k 3 4fc u 



These mixtures represented different kinds of earth, in 

 each volume of which the third contained one-fourth, 

 the second one-half the quantity of the nutritive sub- 

 stances present in the first. 



The pure turf contained 2'5 per cent, of nitrogen, 

 and 100 grammes yielded 4'4 grammes of ash, which, 

 upon analysis, were found to contain 0*115 gramme of 

 potash, 0-0576 gramme of phosphoric acid, besides lime, 

 sesquioxide of iron, silicic acid, magnesia, sulphuric 

 acid, and soda. (See more fully in Appendix E.) 



With each of these mixtures a pot was filled, each 

 pot holding 8% litres (2592 grammes, 39917 grs.) ; a 

 fourth pot, of similar size, contained dry turf-powder. 



Taking into consideration the amount of ash in 

 ordinary turf, the four pots severally contained the fol- 

 lowing quantities of nutritive substances : 



