156 THE YEAR-BOOK OF AGRICULTURE. 



effect upon vegetation. The next ingredient in fish was the oil. The proportion of this 

 differs very much in different fish. In the flesh of the herring, 13 per cent, had been found. 

 In the mackerel, Prof. Way had found as much as 24 J per cent, of oil, or one-fourth part of 

 its entire weight. In this fish the oil seemed to substitute part of the water found in other 

 varieties ; for it did not contain more than 44 per cent, of moisture, or two-thirds of that 

 usually present. The quantity of nitrogen and of ash was also very large ; both of them 

 very considerably larger than in any other fish of which the comparison was known. If 

 available in quantities, therefore, this fish would be very valuable for manure. Now, con- 

 sidering the large proportion of oil in fish, it became important to consider of what value it 

 might be in manure. It had become the fashion of late years to give too exclusive a con- 

 sideration to the importance of nitrogen in vegetation ; not that we could too much value this 

 important element, but that we were in danger of neglecting those substances which took a 

 less prominent, but a no less necessary part, in the economy of vegetation. That carbona- 

 ceous matter in the soil was beneficial, if not indispensable, to profitable cultivation, did not 

 seem to admit of a doubt; and if so, there might be clearly a choice between carbonaceous 

 substances, according to their rate of decomposition, &c. Now oils were very susceptible 

 of oxidation, with the production, of course, of carbonic acid. He might only mention in 

 illustration, the spontaneous combustion often occurring when oily rags used for machinery, 

 &c. had been thrown into a heap, and by the absorption of oxygen and heat consequent 

 thereupon, it had, in many cases, caused great destruction of property. 



Then again, the manufacture of "drying oils," as they were called, by boiling linseed and 

 other oils in contact with the air, the experiments of Saussure, who placed different oils 

 under receivers of air, and found at the end of the experiments that all the oxygen had 

 become carbonic acid at the expense of the oil, were also *o the purpose. Now it was easy 

 to see that oil distributed through a porous soil would, on account of the great surface 

 exposed, suffer rapid oxidation, and give off a ready supply of carbonic acid, which at par- 

 ticular periods of their growth might be most important to some plants. 



Mr. Way quoted passages from the work of Dr. Home, printed in 1762, and the "Georgical 

 Essays" of Dr. Hunter, a few years later, to show that a very high opinion of the value of 

 oil as manure was held by early writers. He also referred to the experiments of Earl Spen- 

 cer with oil, to the use of whale-blubber, which, however, no doubt owed much of its value 

 to the flesh. He showed also that many of the substances known as powerful manures, and 

 containing nitrogenous matter, also contained oil. Thus woollen rags, rape-cake., &c. might 

 owe part of their efficacy to this cause. Rape-cake contained about 4 per cent, of nitrogen, 

 while its oil varied from 12 to 15 per cent. 



On the whole, this subject of oil, as manure., was well worth looking into ; not that oil 

 would be likely to be used directly as a manure, (its value for other purposes being opposed 

 to such a use of it,) but that we might be able to value more correctly substances in which 

 occurred, and could not profitably be extracted, as suitable for manure. The other main 

 ingredient of fish was the ash or mineral matter, which, although of less importance than 

 the others, (on account of the smallness of its proportion,) was not to be overlooked. Mr. 

 Way here referred to the analyses of different fish, showing that in the lobster the quantity 

 of phosphate of lime was as much as 5 per cent, of the fish in its dried state, and about the 

 same in the mackerel : this phosphate of lime could not be without its use. 



Mr. Way next directed attention to the various methods of preserving fish that had been 

 proposed, including those of Mr. Petit, by sulphuric acid; of Mr. Elliott, by the use of alkali ; 

 of Mr. Bethell, by the employment of tar-oils; and of M. de Molons, by treatment with high- 

 pressure steam. He also mentionod the plan which was adopted by a manufacturer of 

 manure, (Mr. Stevens,) who had a contract for the refuse fish of Billingsgate market, of incor- 

 porating the fish in super-phosphate of lime, the quantity of water in the fish serving to 

 dilute the acid, and being dried up by the natural heat of the process. He remarked, how- 

 ever, that there would be no difficulty in preserving the fish, if it could be obtained. It was 

 not so much a question of this or that process, but of the supply of raw material. He could 

 not help believing that this was not an insuperable difficulty, if systematic measures were 

 taken to effect the purpose. Was it affirmed that our system of taking fish was incapable of 



