212 Composition and Value of Guano. 



A number which does not differ greatly from that deduced from 

 the last series of analyses. 



The highest per centage of phosphate of lime is .63*5 

 The lowest ,, ,, ,, „ . 51-0 



The mean of 11 specimens . . . .57*4 



Exhibiting also a tolerably close resemblance to that of the 

 other analyses, and furnishing satisfactory proof of the trustworthi- 

 ness of both sets. 



As a summary of the preceding analyses it may be interesting 

 to give here the average proportion of ammonia and phosphate of 

 lime contained in the different varieties which have been ex- 

 amined. 



The ammonia is as follows : — 



In Peruvian Guano (32 specimens) . 17*41 per cent. 



Jchaboe . (11 specimens) . 7*30 ,, 



Patagonian . (14 specimens) . 2*54 „ 



Saldanha Bay (20 specimens) . 1*62 ,, 



The phosphate of lime in the same number of specimens : — 



Peruvian Guano . . . 24*12 per cent. 



Ichaboe . . . . 30*30 „ 



Patagonian . . . . 44*60 „ 



Saldanha Bay .... 56*40 ,, 



In these figures are interestingly apparent the changes which 

 have occurred in the varieties which originally (that is to say, as 

 deposited by the birds) w^ere, in all probability, nearly identical. 

 Every ton of Saldanha Bay guano may, indeed, be regarded as 

 having; orio;inated from two or more tons of Peruvian, from which 

 fermentation and rain have removed the greater part of its ammo- 

 niacal compounds. 



Having now at our disposal the analyses of a great many speci- 

 mens of the different varieties of guano, we are in a condition to 

 apply our knowledge to the question of their money-value. It is, 

 however, to the Peruvian guano that the reader's attention will be 

 principally directed ; for although a certain limited quantity of 

 the other varieties is still in the market, it is understood that no 

 great supplies are henceforth to be expected, except in the case 

 of the Peruvian guano. It is highly satisfactory to hear that the 

 mountains of the latter are practically inexhaustible. 



A knowledge of the composition of the inferior kinds will, how- 

 ever, prove useful, not only as exhibiting the points of relation 

 between composition and the public appreciation which fixes the 

 selling price, but as furnishing data for the calculations upon 

 which we are about to enter. 



Our present object is, by an examination of the different com- 

 mercial sources of the fertilizing ingredients in guano, and of the 

 cost at which they can be supplied in this or that compound — to 



