TRACTS ON VARIOUS SUBJECTS, &c. 21 



Founds. 

 1st. The guana :* or, sea-fowl dung- at 35 bushels per 



acre, yielded - - 639 



2d. Horse dung litter at 35 cart loads or 420 bushels 



per acre, yielded _ _ _ q26 



3d. Hog's dung litter, at 35 cart loads, or 420 bushels 



per acre, yielded _ _ _ 534 



4th. No manure - - - - 446 



Total pounds - 2245 



* The guana or sea-fowl dung, which is found in considerable quantities upon Egg 

 Island, was first recommended to my notice by the Right Honourable Sir Joseph Banks, 

 President of the Royal Society. " It furnishes," says he, " the loading of an immense 

 " number of vessels that are constantly employed in bringing it from small islands, to the 

 " main land on the western coast of South America, where it is sold and distributed for 

 " the purpose of manure ; which it answers, in a degree, infinitely superior to any other 

 " article we have the knowledge of. — A handful is considered as sufficient for several 

 " square yards of land, the produce of which is exuberant, in consequence of the force of 

 " this amplication." 



The accuracy of this valuable communication has been most amply confirmed by my 

 experiments in the culture of potatoes, as well as upon grass lands. Thirty-five bushels 

 of the guana, or tliree eart loads per acre, appear to n]e, equivalent in efifect, to seventy 

 loads of good rot-dung. I should imagine that abundance of this most valuable manure 

 might be liad from many of the rocks and islands on the coasts of Scotland. 



The efifect of the guana upon grass land is comparatively greater than in the potatoe 

 experiments. — From what cause this proceeds it may be difficult to explain : but as Dr. 

 Priestley found, by exp<riment, that vegetables throve best when they were made to grow 

 in air made putrid by the decompcjsition of animal and vegetable substances, it may be 

 inferred that the very strong effluvia which issues from the sea-fowl dung, or guana, toge- 

 ther with its being readily washed among the roots of vegetables by the first falls of rain, 

 are circumstances that may possibly render its effects, as a top dressing, greatly superior 

 to those it produces when it is mixed with tiie soil. By this mixture its powers may be 

 v/eakened, and a great portion of effluvia, which by some is supposed the proper food of 

 plants, being retained underground, cannot escape and unite with the atmosphere. 



On the 29th of July, 1808, I marked out a space, on the lawn in front of Plantation- 



