172 Experiments upon Swedes. 



phosphoric, instead of three equivalents of lime and one equiva- 

 lent of phosplioric acid as in the ordinary bone-phosphate. 

 Originally this guano does not contain any appreciable amount 

 of soluble phosphate, but chiefly consists of bi-basic phosphate 

 of lime, and as this phosphate requires only one equivalent 

 of sulphuric acid to be rendered soluble or converted into 

 bi-phosphate of lime, whereas the ordinary bone-phosphate 

 requires two equivalents of sulphuric acid for this purpose, a 

 valuable and highly concentrated manure can be prepared from 

 it with less expenditure of sulphuric acid than is requisite in 

 changing other phosphatic materials, such as bone-ash, coprolites, 

 &c., into soluble phosphates. This circumstance fully accounts 

 for the comparatively small quantity of sulphate of lime which 

 this fertilizer contains. 



Plot II. — Manured with phospho-Peruvian guano. No. 2, at the 

 rate of 3 cwt. per acre. 



Produce 8 tons 9 cwt. 2 qrs. 2 lbs. 



Increase per acre .. 1 tea 17 cwt. 3 qrs. 6 lbs. 



The tops of this plot were not quite so large as those in No. I. 

 The plants grew very vigorously at first, but like all the other 

 plots received a sudden check by the extremely warm and dry 

 weather in August. 



An analysis of the guano used in this experiment gave the 

 following results : — 



Composition of Phosplto-Peruvian Guano, No. 2. 



Moisture 15*42 



* Organic matter and ammouiacal salts 3'85 



Bi-phosphate of lime ir)"22 



Equal to bone-earth, rendered soluble by acid .. .. (2o'74) 



Insoluble ])hosphates, (Phosphoric acid .. 13-73) 04^.4.1 



consisting of : .. I Lime 10"G8i 



Hydrated sulphate of lime 32-13 



Alkaline salts 1-87 



Insoluble silicious matter 7'10 



loo-oo 



* Containing nitrogen -40 



Equal to aminonia •4!) 



Percentaji,e of phosphates, rendered soluble by acid .. .. 23-74 



of insoluble phosphates, calculated as bone-earth 



(tiibasic phosphates, 3 Ca O, + P O5 ) 



f^l 2 



9-74 



Total percentage of phosphates calculated as tribasic) 53.43 

 phosphates / 



In this sample of phospho-Peruvian guano the proportion of 

 soluble phosphate is larger than in the preceding, and the total 

 amount of phosphates in both is about the same. There is a 



