AND TPIE SUBSTITUTES FOR OIL-CAKES. 67 



seeds of weeds, seeds of inferior nutritive value, which some- 

 times possess deleterious properties ; whilst in English cake 

 such seeds are, comparatively speaking, few in number, or are 

 altogether absent. Now the comparative absence of such foreign 

 seeds in English cake is another reason of its superiority. Then 

 another circumstance is to be taken into account in forming a 

 correct estimate of the differences we find to prevail in linseed- 

 cake. We have to bear in mind and to examine whether the cake 

 has been hot-pressed or cold-pressed. Cold-pressed cake that 

 is, cake to which no heat has been applied in pressing out the 

 oil from the linseed keeps better and is more palatable than 

 hot-pressed cake. Heat used for expressing oil from linseed 

 alters, in a considerable degree, the remaining portion of oil in 

 the cake, as well as other constituents, more especially the albu- 

 minous matters in cake. We know very well that in boiling 

 albumen coagulates ; and inasmuch as linseed contains a con- 

 siderable quantity of albumen, or substances closely allied to 

 albumen, heat applied to the seed coagulates the albumen, and 

 the higher the heat has been applied the more thoroughly it 

 coagulates. In consequence of this the cake becomes less digestible 

 just like a hard-boiled egg is indigestible. But it is not only 

 the coagulation that causes the difference in the quality of hot- 

 pressed cake, but it also alters the mucilage and gum which exist 

 therein. When too strong a heat is applied in the process, cake 

 loses its gelatinous properties altogether, or, at any rate, in a 

 great measure ; whilst good cake, when mixed with cold water, 

 becomes very gelatinous. 



And this leads me, in the next place, to make a few observa- 

 tions on the modes of examining, practically, the quality of 

 linseed-cake. The result of a great many examinations, which 

 I have made quite recently, has shown me that it is not generally 

 desirable to submit cake to chemical analysis. The practical 

 farmer may save himself the trouble and expense of an analysis, 

 inasmuch as he has the means at hand of examining for himself 

 whether the cake is of a superior or inferior character. A 

 number of experiments I have made with the view of finding 

 out for the practical man an easy method for examining this 

 cake have given me the following result as the best plan. I 

 would recommend you to proceed as follows : Take about a 

 half an ounce of cake, powder it roughly in pieces, mix it in a 

 tumbler or in a jug with six fluid ounces of water, and leave the 

 whole (stirring it occasionally) for about 12 hours. The best 

 cake, after that time, renders the quantity of water just mentioned 

 particularly gelatinous, so that the water hardly separates from 

 the jelly ; whilst interior cake renders water much loss gelatinous, 

 and in standing separates a much larger bulk of water. 



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