no CHEMICAL FERTILIZERS 



cake can be fed in small quantities, it is liable to be contami- 

 nated with mustard, when it becomes very unsuitable for 

 feeding. By breaking the resulting cake into dust, a much 

 more suitable article for manurial purposes can be obtained. 

 There is a popular idea that rape cake is useful for pre- 

 venting the ravages of wire worm. It has been used at 

 both Rothamsted and Woburn as a top dressing for wheat 

 and barley, where it has proved a most effective material. 

 Since the introduction of extractive methods of obtaining 

 oil, a very large quantity of rape seed is now extracted with 

 " benzine," and an extracted meal made from rape by this 

 process is sold under the name of " Homco." The cake 

 contains about 5 or 6 % of phosphates with i or 2 % of potash. 

 Fish Manure. The sea has an inexhaustible supply of 

 fertilizing materials. Apart from its own richness, it is 

 constantly receiving organic matter from other sources. 

 These materials all help to maintain the marvellous fertility 

 of the sea. Possibly one of the reasons why the herrings 

 have left the Baltic and approached the British Isles is 

 the greatly increased population of the British Isles, and 

 the large quantity of refuse which is consequently dumped 

 into the sea. Various forms of vegetation in the sea are 

 thereby encouraged in their development, providing an 

 increasing supply of food for the fishes, which naturally 

 congregate near the source of their chief food supply. 

 During the herring season, when large numbers of fish are 

 caught off the British coast, considerable quantities of fish 

 refuse are obtainable ; there are the heads and tails of the 

 herrings which are cut off before salting; the herrings are 

 generally split and gutted, and it is necessary to dispose of 

 all these waste materials ; there are, in addition, large 

 numbers of worthless fish which are caught along with the 

 useful ones. All these large amounts of material would 

 become offensive in a very short time were they not converted 

 into something harmless ; the large firms controlling the 

 fishing industry have been compelled, in their own interest, 

 to establish large central depots to deal with waste substances. 

 A superior quality of refuse, obtainable from whitefish, is 



