316 BOARD OF AGRICULTURE. 



in citrate of ammonia. Ether abstracted at ordinary tempera- 

 ture 18 per cent, more of a thick, highly-colored, oily mass. 

 The following rules of rendering the fish were stated as being 

 customary in the establishment above mentioned : the fish were 

 boiled for about one-half to three-quarters of an hour, by 

 means of steam of from 70 to 80 pounds' pressure, in large 

 wooden tanks with false bottoms ; and subsequently, after the 

 soup had been withdrawn, subjected to a pressure of about 

 115 to 120 pounds per square inch. The fish mass, in conse- 

 quence of its gelatinous condition, retains usually still from 

 50 to 55 per cent, of moisture. In a large fish-rendering 

 establishment near New York City, I noticed that the boiling 

 of the fish was continued only 25 minutes, with steam of 50 

 pounds' pressure, and the rendered fish mass subsequently 

 treated with 160 pounds' pressure per square inch. 



The soup, which contains besides the oil more or less of the 

 glue-producing, soluble nitrogenous matter of the flesh and 

 the bones, is at present discharged after, by means of settling- 

 tanks, the oil has been carefully removed. This practice 

 causes a considerable waste of nitrogen. The yield of oil 

 difiers, often widely, even during the same season, being, it 

 was stated, usually highest during autumn. The rendering 

 begins usually in May or June, and closes late in the fall. 

 The quality of the fish refuse in general, independent of its 

 moisture and mechanical condition, depends quite naturally 

 to a large extent on the following circumstances : — 



First, On the kind used, and whether entire or in part. 

 Second. On the peculiar mode of rendering. 

 Third. On the time when the fish are caught. 

 Fourth. The course pursued in keeping and preparing the 

 refuse for the general market. 



Each of these circumstances exerts an influence of its own 

 on the composition of the fish guano. 



Judging from general appearances, but little attention is 

 paid thus far to the first three conditions ; the influence of the 

 last one is, more or less, fully understood, yet not satisfactorily 

 controlled. A main difficulty, no doubt, arises from the 

 irregular arrival of large quantities of fish at one time during 



