Composition and Value of Guano. 227 



APPENDIX AND NOTES. 



1. On the Sampling of Guano. — In taking samples for analysis the fol- 

 lowing plan was followed : — When taken from the ship, a complete mix- 

 ture of the guano from several parts of the cargo, to the extent of perhaps 

 half a cwt., was made in the vessel itself. From this heap a quantity of 

 2 or 3 lbs. was removed to the laboratory for analysis. If the cargo was 

 in the warehouses, The mixture was made from the centre of several bags 

 which were cut open for that purpose. In the selection of the sample, "if 

 a lump of any sort shoukl occur, appearing to bear too large a proportion 

 to the whole mass, it is rejected. 



To prepare the guano for analysis, the sample of 2 or 3 lbs. is made to 

 pass, by rubbing in an iron mortar, through a vdre sieve of 40 holes to the 

 square inch ; it is afterwards thoroughly mixed by continued rubbing in 

 the mortar. From the mixture so made a quantity of about an ounce is 

 separated, and carefully powdered in an agate mortar. This last forms the 

 subject of the analysis. 



In the course of the analyses which are given in this paper many cases 

 have occurred tending to prove that a sample of guano taken in this v/ay 

 fairly represents the bulk from which it is separated. One or two in- 

 stances may be mentioned. In Table 3 the specimens 12 and 13 are 

 duphcates. No. 12 was taken from two or three bags ; No. 13 was a mix- 

 ture of portions taken from more than 100 bags. By an inspection of the 

 Table it will be seen that the differences between the two samples are by 

 no means large. In Table 6 are tv^^o specimens of "Parkfield" (3G and 

 40.) These samples were taken at different times, but closely resemble each 

 other. 



Then again, in Table 5, specimens 28 and 29, as also 30 and 31, are dupli- 

 cates. A glance at the analyses will show that they are very much alike, 

 although the samples were taken at two different periods during the un- 

 loading of the cargo. 



In order to ascertain to what extent the different parts of a sample of 

 guano would possess a difference of composition, I made the following 

 experiment: — A mixture of many different specimens of Peruvian guano 

 which had from time to time reached the laboratory, and in the same state 

 as when taken from the ships, was sifted successively on sieves of 40 and 

 20 holes to the inch. In this way three separate samples of different de- 

 grees of fineness were obtained : — 



No. 1, passing the 40-hole sieve. 



No. 2, passing the 20, but retained by the 40-hole sieve. 



No. 3, which v^^as too large to pass either. 



In the latter the lumps, which were tolerably hard, were of various sizes, 

 some being as big as pigeons' eggs. The three siftings were separately 

 powdered and partially analysed, with the following results : — 



Water. Organic Matter, &c. Ammonia, 



No. 1. . . 11-19 per cent. .. 53-42 per cent. .. 17-28 per cent. 



No. 2. . . 12-19 .. 51-94 .. not ascertained 



No. 3. . . 11-00 .. 53-93 .. 16--iO 



This experiment affords very strong evidence in favour of a great amount 

 of uniformity, even where small specimens only are compared. It shows 

 that the white lumps are really only agglomerations of the smaller particles, 

 and that indeed they are no richer Ihan the latter. This remark only 



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