CHAKACTERISTICS OF GOOD OIL-CAKE. 321 



On examining the sample, it was at once apparent that 

 notwithstanding these results it was extremely impure, 

 and contained a large quantity of grass and other seeds, 

 amongst which I detected some grains of what appeared 

 to be blighted rye. Owing to the general similarity in 

 composition of many kinds of seeds, it is perfectly possible 

 that an oil-cake may be adulterated to a very considerable 

 extent without its being apparent in the analysis, and 

 hence it is necessary to submit the sample to a very care- 

 ful examination before forming an opinion on this point. 

 The question of the adulteration of linseed-cake is con- 

 siderably narrowed by an important commercial consider- 

 ation. It yields an oil distinguished by its tendency to 

 harden into a solid varnish, and hence is called a "drying" 

 oil ; and it is impossible to adulterate this oil with any 

 other without producing such a deterioration of its charac- 

 teristic properties as to be immediately obvious. Hence 

 linseed oil-cake is never adulterated with any other kind 

 of oil-seed ; but when an admixture occurs, it is usually 

 with some cheap non-oleaginous seed, and most generally 

 with grass seeds. In the great majority of instances in 

 which this occurs the seeds have not been added as a 

 deliberate adulteration, but are due to the careless cultiva- 

 tion of much of the linseed used abroad. It is difficult, of 

 course, to form an opinion as to where inferiority due to 

 dirty seed ceases and positive adulteration begins, nor is 

 the determination a matter of much importance in a prac- 

 tical point of view. In judging, therefore, of the goodness 

 of a cake, attention must be paid to its general appear- 

 ance. It should be a hard, well-pressed cake, with no 

 tendency to split into layers. Its colour should be reddish, 

 and when broken across its appearance should be uniform, 

 and the smooth and glistening outer coat of the seed 

 should be apparent. It should then be carefully examined 

 for foreign seeds. AmoDg these are frequently found 



