266 FERTILIZERS. 



rect application of fertilizers. The time, however, has come -when more attention is required 

 to lands in pasture. 



10. Guano. 



The excrementitious matter of birds, in consequence of their peculiar iruucture, furnishes 

 a mixture of substances rich in all those which are active in promoting vegetati ■ : it is the 

 richest of fertilizers, under favorable circumstances. The history of guano is lii.i-.c^iing, par- 

 ticularly so if taken in connection with the places of deposit. To us, who inhabit a country 

 upon which rains never fail, in their season, it is a matter of surprise, when we learn, for 

 the tirst time, that there are countries where it never rains. It is in those countries that the 

 guano is found. The biYds, which are large and numerous, and which Subsist upon fish, have 

 inhabited the islands, upon or near the main coast, from the remotest time ; consequently, during 

 the centuries which have elapsed, there are accumulations of guano to a vast extent. It is the 

 most highly aniraalized substance, being, in reality, derived entirely from animal substances ; 

 accumulating slowly in thin layers, time is furnished for its partial drying, otherwise, if it was 

 produced in large heaps, it would heat by fermentation, and prove nearly worthless. Guano 

 is composed of the following elements : 



Organic matter, 56 "00 



Phosphates of lime and magnesia, 26-00 



Carbonate of lime, 6 '00 



Salts of soda, 10-00 



Salts of potash, trace. 



Silicious matter, 2-00 Johnston. 



The ammonia is variable ; in the Ichaboe guano it does not exceed 6 o.- 8 per cent. From 

 the nature of animal matters, it follows that ammonia, which is essentially volatile, must be lost 

 in all the changes which this substance undergoes, spontaneously ; and hence the varieties, as 

 those from different localities will vary in the amount of ammonia which they contain, and even 

 will vary in samples from the same place. For this reason, too, the composition which has 

 just been stated does not fully represent the condition of guano, as it reaches our shores : oxa- 

 late, carbonate, phosphate and sulphate of ammonia should be added. The carbonate of am- 

 monia is volatile, but the sulphate is fixed. These are important substances, and being soluble, 

 act at once upon vegetation. To determine the presence of ammonia in guano, add quicklime 

 to a sample, when, if present, it will be exhaled in the peculiar pungent fumes, known to all 

 persons. Tiie most economical quantity, for an acre of land, varies from three to five hundred 

 pounds. It is one of the peculiarities of this substance that, if applied in large doses, it injures 

 rather than benefits the crop ; ahd, indeed, it is so active that seeds should not be enveloped in 

 it at all, as it destroys, or is very liable to destroy their vitality. Many failures have occurred 

 in the use of guano ; they have arisen from too free an application, and also from drought. A 

 dry season is unfavorable to the employment of it ; as, in that case, it is not dissolved, and 



