550 On the Treattnont of Decaj/pd Poiatoes, Si^c. 
A'arieties. 
I cwt. Seed 
protlucGtl 
One statute 
Acre 
produced 
100 parts contained 
Water. 
Starcli. 
Ciluten 
and Fibre. 
Cwt. 
Tons. 
. Rohan 
58 
14i 
1 fi'fi 
1 U \J 
ft • 9 
Large Yellow 
37 
9f 
68-7 
23-3 
8-0 
Scotch 
32 
8 
69-8 
22-0 
8-2 
Slow Island . 
56 
14 
•79-4 
12-3 
8-3 
Legonzac 
32 
8 
H-2 
20-5 
8-3 
Siberian . 
40 
10 
17-8 
14-0 
8-2 
Durillers . 
40 
10 
78-3 
13-6 
8-1 
All of you are familiar with the process of procuring: starch 
from the potato. It consists simply in grating down the tuber 
and washing it with water. The starch, as shown in the previous 
lecture, is imprisoned within cells ; and in grating down the 
potato we tear down the walls of the cells and liberate the little 
granules of starch. These are insoluble in cold water, and 
generally are not larger than the Yfirth of an inch in diameter ; 
consequently, when we pour upon coarse cloth the grated 
mass stirred up and suspended in water, these small globules will 
pass through while the woody fibre and other constituents of the 
cell walls are retained on the cloth. The starch which has 
passed through still continues coloured by a little of the diseased 
matter, but this may be removed by three or four washings and 
depositions. This starch, after having been dried, may be pre- 
served for any length of time.* The residual pulp remaining 
on the cloth contains still a large proportion of nutritious matter, 
which becomes easily putrid and occasions a considerable nuisance 
in the neighbourhood of large starch manufactories. In Paris the 
nuisance of this was so great, that endeavours were made to con- 
vert it into some practical use, and it was found that in this 
advanced stage of decomposition, it formed an admirable man-ure 
for land, especially Avhen applied in the liquid form by irrigation. 
More lately it has been used for feeding cattle with good results ; 
nor will this be surprising, when we remember that it contains all 
the insoluble gluten of the potato. An analj'sis of the dried 
pulp thus procured showed that it contains 6 per cent, of gluten, 
which gives it about half the nutritious value of oats. Of cour.se 
our great care should be to economise the greatest quantity of the 
valuable ingredients of the diseased potato. Now if the pulp can 
* I have thought it unnecessary 1o enter into any detailed account of 
the manulacturo of starch, as this is now practically carried into execution 
in eveiy part of the country. 
