HISTORY OF THE AMERICAN MENHADEN. 221 



fully removed. This practice causes a considerable waste oi" nitrogen. 

 The yield of oil differs, 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 con- 

 dition, depends, quite naturally, to a large extent, on the following cir- 

 cumstances : 



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



"Second. On the peculiar mode of rendering. 



"Third. On the time when the,tish 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 diffi- 

 culty, no doubt, arises from the irregular arrival of large quantities offish 

 at one time during the season ; and the means, which are at present 

 usually employed to meet this difficulty, are, quite frequently, inadequate 

 to the demand. Many manufacturers of fish-oil consider it, therefore, 

 apparently a safer proceeding to dispose at once of their crude stock at 

 low rates than to run the risk any longer. Without questioning the 

 soundness of their course of action, in case of limited pecuniary means, 

 there seems to be no valid reason why improvements should cease here 

 as long as it is daily demonstrated that it pays well to collect animal re- 

 fuse matters from all over the country and to work them into valuable 

 concentrated fertilizers. 



" Nobody familiar with the nature of a good fish guano considers it less 

 efiQcient for agricultural i)urposes than any other animal refuse matter 

 of a corresponding percentage of phosphoric acid and nitrogen. In fact, 

 all true guanos, the Peruvian not excepted, owe their most valuable 

 constituents, in a controlling degree, directly or indirectly to the fish. 



"Our fish guano consists of the entire body of the menhaden fish, 

 which has been deprived purposely of its main portion of fat, and, inci- 

 dentally, more or less completely df its soluble nitrogenous matter. The 

 more the flesh predominates, the more the fat has been abstracted with- 

 out the application of an excessive heat, as far as time and degree are 

 concerned, the higher will be the commercial value of the residue of the 

 press in case of an equal percentage of moisture. The flesh of the fish, 

 like that of our domesticated animals, contains on an average 15 per 

 cent, of nitrogen. The same close approximate relation exists between 

 the bones and the textures of these otherwise widely differing classes of 

 animals; for the fish-bones and the scales consist, mainly, of a varying 

 quantity of cartilaginous (nitrogenous) matter and of (tricalcic phos- 

 phate) bone phosphate. 



