282 BRITISH HUSBANDRY. [Ch. XXII. 



PRODUCE VALUE, AND APPLICATION. 



The potato growers about London usually reckon upon crops of eight 

 to ten tons per acre ; and the ox-noble and other large sorts will occasion- 

 ally yield as much as twelve tons. This, it must however be observed, can 

 onlybe calculated upon in situations which command an unhmited supply 

 of dung, and on soils which have been ameliorated by a long course of 

 careful cultivation. The accounts given of produce are indeed so various, 

 that no specific estimate can be formed without classing the difl'erent 

 varieties of species, soil, and management ; but, generally speaking, we 

 should be rather inclined to assume the average of crops on land ot tair 

 ordinary quality, and under the common system of iarming, as not amount- 

 ing to more than from six to eight tons, or about 200 to 250 bushels. The 

 ton is usually calculated at 3'2 bushels of 70 lbs. each, which is the exact 

 weight ; but heaped measure will sometimes yield more ; and in some 

 places 3G bushels are reckoned to the ton. 



It has been found by chemists, that in every 100 parts of the potato 

 tliere are about 70 parts of water and 30 of potato-meal, which is a 

 powder of a rather greyish colour, retaining slightly the taste of the raw 

 tuber. This shows that the quantity of water contained in the roots when 

 raw is much greater than usually supposed, and proves the pro[)riety of 

 steaming them for the use of cattle. According to an analysis made by Sir 

 Humphry Davy*, the avoirdupois pound of 7000 grains of the black kid- 

 ney potato contained — 



Of soluble mucilage . . grains, 970 



Of pure starch . . • 695 



Of fibre .... 622 



Of water .... 4713 



and the quantity of nutritive matter contained in 64 drachms of the follow- 

 ing species, was — 



In the cliampion . . . grains^ 260 



In the hundred-eyed . . 218 



In rough-red ... 204 



In purple-red . . . 200 



In ox-noble .... 195 



Although failures have recently occurred to a wide extent in the crops 

 of potatoes, yet there is perhaps no vegetable of which the produce has 

 been usually considered so certain ; and it has the advantage of being most 

 abundant in those wet seasons which render corn crops so defective. It 

 usually, indeed, bears a certain ratio to the price of wheat, as 4 lbs. of a 

 good quality contain as much nutritive matter as 1 lb. of wheat, and the 

 demand is such, as always to leave a fair profit to the grower in the vicinity 

 of laro-e towns ; but the cost of manure and the expenses of culture are so 

 high, that unless in such situations, or in those which possess advantage of 

 water-carriao-e to a market, and which therefore do not confine its consump- 

 tion to the tenants of the homestead, it can seldom repay its cultivation on 

 a large scale. In most cases, liowever, it uill be found advantageous to 

 grow a quantity proportionate to the number of bullocks or other large 

 stock maintained u])on the farm ; for it frequently happens that, when kept 

 on turni]:)s, the crops fail through circumstances which cannot be foreseen, 

 and considerable expense is then incurred, by the. necessity of having re- 

 course to the hay-stack, or to oil-cake, to keep the cattle in condition. The 

 loss thus occasioned may be saved by the growth of potatoeis ; and, even if 



* See Sinclair's Iloit, Grain, Woburn. p. 409, 



