a>:d manure kept ua'dek cover. 283 



manure to a great extent. If the courts were covered, and the 

 rain all run off, the sewerage would be mixed along with the dung, 

 thus the greater strength would be obtained. A great deal of 

 ammonia must be lost from the dung w^hen the sewerage is all 

 run away, which must assist the crops for the hrst year at least ; 

 and I have invariably observed that one good crop follows 

 another even with the same treatment. 



EXPERIMENTS ON POTATOES WITH DIFFERENT MANURES. 



By Russell Swaxwick, ;M.R.A.C., Cirencester, and E. W. Pretost, Ph.D. 

 F.R.S.E., late Professor of Chemistry in the Royal Agricultural College, 

 Cirencester. 



[Premium — Tivo Medium Gold Medals.'] 



Part I. 



These experiments were conducted by Dr. E. W. Prevost and 

 myself jointly, he kindly undertaking the lion's share of the 

 work — namely, the whole of the chemical and analytical work, 

 amounting to not less than twenty-five complete analyses, which 

 in many cases were made in duplicate ; also all the weighings 

 and preparation of the various manures for each plot, an account 

 of which appears in the second portion of this report. ]\Iy 

 bailiti' (Mr. Putlierford) assisted in the applications of the 

 manures, and superintended the w^eighings of the potato crop 

 with most minute care. 



Thirteen years of potato-growing on this farm, and many 

 previous experiments, lead me to suggest certain combinations of 

 manures calculated to be most useful, and to supply a crucial 

 test as to which would produce the best results ; others were 

 added by JJr. Prevost as having some scientific as well as 

 practical interest, and as likely to effect the composition of the 

 tuber. When Dr. Pievost su«jijested the crreat interest and value 

 of a careful estimate of the starch in samples from each applica- 

 tion I imagined it could be easily done by determining the 

 specific gravity, and I hiul no idea of the large amount of lal)our 

 he was entailing upon himself in making an actual complete 

 analysis of fifteen samples of potatoes. Tlie interest of these 

 chemical results, however, lias quite recompensed for the labour. 

 I regret, on my part, that I did not keep sanqdes of tlie various 

 plots to test their cooking and eating (lualities, for, with a 

 diU'ereiice of 3 or 4 per cent, in the starch, it woukl certainly 

 have been ])erceptible. When considering these ex])erinients, it 

 was determined that they slunild be tried on a variety of potato 

 which liad liitlierto Ix'cn conipai-atively exempt from disease — 



