ma a 
294 HOW CROPS FEED. 
ered with a luxuriant growth of confervee, which did not 
happen in the other glasses.” (Jour. Roy. Ag. Soe. of 
Eing., X1., 366.) 
Professor Way likewise found that filtering urine 
through clay or simply shaking the two together, allow- 
ing the liquid to clear itself, and pouring it off, sufficed to 
prevent putrefaction, and keep the urine as if fresh for a 
month or more, Cloez found, as stated on p. 264, that in 
a mixture of moistened pumice-stone, carbonate of lime, 
and urea (the nitrogenous principle of urine), no nitrates 
were formed during eight months’ expesure to a slow 
current of air. 
These facts make it necessary to consider in what state 
the nitrogen of urine is absorbed and assimilated by 
vegetation. 
Urine contains a number of compounds rich in nitro-  - 
gen, being derived from the waste ot the food and tissues 
of a numa: which require a brief notice. 
Urea (CO N,H,)* may be obtais.ed from the urine of 
man as a white crystalline mass or in distinct transparent 
rhombic crystals, which remain indefinitely unaltered in 
dry air, and have a cooling, bitterish taste like saltpeter. 
It is a weak base, and chemists have bat si its nitrate, 
oxalate, phuephate ete. 
Urea constitutes 2 to 3 per cent of healthy human 
urine, and a ies and robust man excretes of it 
about 40 grams, or 1"|, oz. ay. daily. 
When urine is left to itself, it shortly emits a putrid 
odor; after a few days or hours the urea it contained en- 
tirely disappears, and the liquid smells powerfully of am- 
monia. Urea, when in contact with the animal matters 
# CArDONG... se tetee e 20.00 
Hydrogen......... 6.67 
NUP OROR . o< ocns 7 hs 46.67 
Oxygen: 23%. 5.5 ee 26.66 
100.00 
