136 Mr. Denham Smith on the Composition of 



On comparing the results of these five analyses, the extreme 

 variableness of the composition of guano is the first thing that 

 demands attention ; no two samples resemble each other: in 

 one, potash salts, abundance of urate of ammonia, with free 

 uric acid exist; in another, the salts of the mixed alkalies are 

 present, but the soda salts in far larger proportion than those 

 of potash, and the amount of urate of ammonia diminished 

 from about 17 to 2 per cent. ; here also free uric acid is absent ; 

 in another instance of ordinary guano. No. 4, no uric acid 

 whatever is present, and this specimen contains a large pro- 

 portion of sand. The amount of ammonia also varies very 

 considerably in this description of guano, and even the pro- 

 portion of those salts which are common to both seldom 

 bear any relation to each other. The state of combination in 

 which the phosphate of lime occurs is also dissimilar ; that of 

 sample No. 1 apparently existing wholly as bone-phosphate, 

 whilst that of No. 2 is a mixture of the neutral with the sub- 

 sesquiphosphate of lime: instances of dissimilarity may readily 

 be multiplied by a glance at the results of these two analyses, 

 the resemblance to each other being for the most part con- 

 fined to the existence of some similar salts in both cases. 



Then, again, the samples of concrete guano differ not 

 merel}' from the common guano, Nos. 1, 2, 3 and 4, but also 

 widely from each other ; sample No. 5, concrete guano, con- 

 taining large proportions of sulphate of soda and oxalate of 

 lime, no uric acid, and but a very small quantity, when com- 

 pared to any of the other samples, of phosphate of lime — this 

 existing in this specimen as bone-phosphate; whilst the other 

 kind of concrete guano, No. 6, affords very small quantities of 

 soluble substances, the merest trace of ammonia salts, and con- 

 sists almost entirely of water and phosphate of lime. The 

 constitution of this salt again varies from that which exists in 

 the specimen No. 5, being chiefly neutral phosphate instead 

 of the bone-phosphate. The saline guano is the very opposite 

 of this last description ; the larger proportion consisting of 

 soda salts and others soluble in water : here also the ammo- 

 niacal salts are almost absent, whilst common salt, a substance 

 existing in comparatively small quantities in the other sam- 

 ples, and totally absent in two of them, is by far its most pre- 

 valent constituent. 



Can we then wonder that such widely differing results should 

 have been obtained by various farmers and experimentalists who 

 have used the substance termed guano ; even when its applica- 

 tion has taken place under almost identical circumstances, as 

 respects quality of land, description of crop, time of application, 

 &c. &c., and differing only in the guano used by either party 



