4 
LETTER OF TRANSMITTAL. 
that station on the changes (nitrification and denitrification) which 
nitrogenous compounds undergo in the soil, and on drainage and well 
waters. These lectures were published in an edition of 5,000 copies 
as Bulletin No. 8 of this Office, but the bulletin is now out of print. 
The second, which was a carefully prepared review of the field and 
feeding experiments at Rothamsted during half a century, by Sir 
Joseph Henry Gilbert, M. A., LL. D., F. R. S., was published in an 
edition of 6,000 copies as Bulletin No. 22 of this Office, and is also out 
of print. 
Respectfully, A. C. True, 
Director. 
Hon. James Wilson, 
Secretary of Agriculture. 
