104 THE POTATO AND ITS COMMERCIAL PRODUCTS. 



advantage over other kinds, that they do not engender worms, and keep 

 fresh for a number of years, provided they are placed in a dry situation 

 and in well-closed vessels. 



A variety of tapioca is prepared from potato-starch by heating the 

 moistened fecula on a copper plate to near the temperature of the boiling 

 point of water. Some of the granules of starch then burst, agglomerate, 

 and form small , hard, and irregular grains, which closely resemble the true 

 tapioca. It is said that potato -starch prepared in October or November is 

 more easily digested than that made in the spring. 



Potato-starch is at present employed to a considerable extent as a sub- 

 stitute for glue in the preparation of size for paper, being usually mixed 

 for that purpose with a small quantity of a solution of resin and carbo- 

 nate of soda in water. This application of starch may be easily detected 

 by moistening the paper with an aqueous solution of iodine, when, if any 

 starch be present, the blue iodide of starch will be formed. 



Potato -starch mixed with chalk, and diluted in a little water, forms a 

 very beautiful and good white for ceilings. This size has no smell, and 

 is more durable. 



The bye-products of the potato-starch manufacture are not without their 

 applications. Thus, the water from which the starch is deposited is well 

 adapted for irrigation. It contains the debris of the pulp, and holds in 

 solution six parts in a thousand of azotised matter. It was formerly an 

 inconvenience to the manufacturer, as it contains a poisonous substance, 

 and produces an evolution of sulphuretted hydrogen gas, if kept a short 

 time, from the decomposition of sulphates by the organic matter. The 

 marc of the pulp which remains after the extraction of the starch is made 

 use of in various ways, as food for pigs, horses, cows, and sheep. It must 

 first be deprived of about half its weight of water by expression ; for if 

 simply drained, it retains too much water to be advantageously eaten by 

 cattle in large quantities. In seasons when fresh alimentary vegetables 

 are abundant, the pulp may be employed as manure ; especially as it then 

 contains a small quantity of solanine, and cannot therefore be given to 

 cattle with impunity. [Parnell.] 



But there are other uses to which this esculent is turned abroad. After 

 extracting the fecida, the pulp is manufactured into ornamental articles, 

 such as picture -frames, snuffboxes, and several descriptions of toys of the 

 papier-mache character. The water that runs from it in the process of 

 manufacture is a most valuable scourer for perfectly cleansing silks and 

 woollens, and such-like articles : it is the housewife's panacea ; and if the 

 washerwoman happens to have chilblains, she becomes cured by the opera- 

 tion. Potato-leaves have been occasionally fraudulently used to adulterate 

 tobacco. 



As the result of our researches, it will be seen that potatoes as a food 

 product come before us in many forms, — as starch, or popularly arrowroot, 

 as sago, semola, vermicelli, and maccaroni ; as polenta ; in the dried and 

 preserved forms, suitable for ship use and transport ; mixed with our bread, 



