312 



On Guano. 



On the other hand, in the identity of the substances contained 

 in guano with those always found in the recent excretions of Hving 

 birds, we have that evidence of a common origin — which in a 

 previous part of the present paper was stated to lend an almost 

 unnecessary confirmation to the evidence there adduced in regard 

 to the source from which the accumulations, on the shores of 

 Peru, have unquestionably been derived. 



One other remark I may here venture to introduce. We are 

 astonished — even geologists, w^ho are familiar with extended 

 periods of time, and are accustomed to contemplate immense 

 results produced by the prolonged action of apparently insig- 

 nificant causes — even geologists are struck with the occurrence on 

 the existing surface of the globe of such vast accumulations of 

 excrementitious matter : yet how are our ideas still further mag- 

 nified in regard both to the number of birds necessary to deposit 

 them, and to the lapse of time during which they must have been 

 gathering, when we learn that what now remains is not — either in 

 bulk or in weight — more than an eighth or a tenth part of that 

 which originally fell from the flocks of living sea-fowl ! 



3. A most important part of the composition of the guano is 

 the quantity of phosphoric acid it contains in combination with 

 ammonia, with soda, and chiefly with lime. All plants require 

 for their healthy growth a portion of this acid in combination with 

 lime. All vegetable productions which unmixed are capable of 

 feeding and nourishing animals must contain it, since from their 

 vegetable food all animals ultimately derive those earthy and 

 other phosphates of w^hich so great a part of their bones consist, 

 and which are also present in smaller quantity in their fleshy 

 parts and in their various fluids. 



The presence of these substances therefore enables the guano 

 to minister to a greater number of the wants of living vegetables 

 than it could do were it entirely composed of uric acid or of 

 ammonia. These latter compounds may abound about the roots 

 and leaves of plants, and yet, if the phosphates be wholly absent, 

 the plant which sprung up of a bright green, and shot forth with 

 vigour, will never attain to a healthy maturity, or produce an 

 adequate return of nourishing food. 



One of the uses served by bones when applied to the land is 

 to yield the phosphate of lime they contain to the successive crops 

 which are grown during an entire rotation. Hence one reason 

 why the effect of bones upon the land is in many cases found to 

 be so very permanent. The animal matter in bone-dust will 



the price usually paid in Flanders for pigeons'-dung. It is there employed 

 as a top-dressing for the flax, and the dung of 100 pigeons is worth about 

 20s. a-year for this purpose— (Sprengel). The injurious effect of recent 

 goose-dung arises from its falling on the grass in too concentrated a state. 

 When diluted by a shower of rain its influence is most beneficial. 



