18 
EXPERIMENTS WITH POTATOES. 
posed, the following experiments were tried; the same sam¬ 
ple of potatoes (Lady of London) being used in each case. 
Only the per cent, of starch in the potato was estimated, 
as, other things being equal, the greater the per cent, of 
starch, the greater their nutritive value; the richer in 
starch, the poorer, generally, in protein; the more watery 
it is, the less the percentage of starch and the greater, as 
a rule, is the amount of protein, and, usually, also of ash. 
Grown in a very rich soil, or in a wet place, the same 
variety of potato contains far less starch, but is richer in 
protein than when grown in sandy soil or a sandy loam. 
Manuring generally lessens the percentage of starch and 
increases the percentage of protein. The ash of the po¬ 
tato contains considerable phosphoric acid and is rich in 
potash, but has only a little lime and soda; this must be 
borne in mind when they are used for feeding milch cows 
or young and growing animals. The following table 
gives the composition of the ash : 
Carbonic anhydride_21.06 
Sulphuric anhydride_2.77 
Phosphoric anhydride_5.72 
Potash_53.47 
Soda_Trace 
Chloride of Sodium_Trace 
Calcic carbonate_ .84 
Magnesic carbonate_3.53 
Calcic sulphate_Trace 
Tri-calcic phosphate_3.36 
Tri-magnesic phosphate_9.25 
Basic ferric phosphate_Trace 
Silica_Trace 
Total_100 
First —In regard to the time the potatoes were on the 
water bath, all the other conditions being alike : 
Time of heating. Per cent, of starch. 
1 hour_17.79 
2 hours_17.78 
3 hours_17.74 
6 hours_17.70 
9 hours_17.20 
