AS A MANURE FOR POTATOES. 263 
The portability of Guano gives it a decided ad- 
vantage, as 5 ewt. of African, at 8s. per cwt. is 
sufficient for an acre of potatoes; while 40 tons 
of night-soil will be required for the same purpose. 
This will cost, at a distance of 8 or 9 miles from 
Manchester 5s. per ton, while horse-dung is much 
dearer, and is frequently ineffective in fertilizing 
power, from imperfect decomposition, and the 
consequent loss of its volatile principles. It will, 
however, be necessary to add fresh Guano with 
every additional crop; as it does not appear to 
possess those qualities of permanency when appli- 
ed to wheat, rye, and the other cereal grains, or 
to grass land. Juan and Ulloa state “ that it is 
not used for wheat and barley, but when applied 
to fields sown with maize, and with proper water- 
ings, it is found greatly to fertilize the soil; a 
little of it being put close to every stem, and im- 
mediately watered.” 
Horse-manure and night-soil, may have their 
volatile principles retained by the admixture of 
chemical substances. Dr. Daubeny states, (Lec- 
tures on Agriculture,) “that night-soil may be 
rendered both inoffensive and portable, by admix- 
ture with animal charcoal, obtained from the re- 
fuse of the sugar refiners,” And, ‘when we re- 
