and from the North Coast of Scotland. 317 



crements of birds, without exception, when first voided, are 

 rich in ammoniacal compounds, and contain more or less of 

 phosphate of lime, birds, generally, must be admitted to be 

 fertilizers — the effect being in proportion to their numbers, — 

 in the instance of the solitary bird not perceptible, but in that 

 of gregarious birds, especially in their roosting-places, very 

 manifest. I have examined the soil under rookeries, and have 

 detected in it ammonia and phosphate of lime. And as, under 

 old rookeries, there must be an accumulation of the insoluble 

 salts derived from the excrements of these birds, it hardly al- 

 lows of question, that it will be advantageous to collect the 

 soil so impregnated, from time to time, at proper intervals, 

 and to employ it as a manure, restoring in this form to the 

 fields a great part of what was taken from them by these use- 

 ful birds, in the shape of worms and grubs. It is a pleasing 

 circumstance in the economy of nature, that the sheltering 

 shrub or tree, and the sheltered bird, benefit each other; 

 that the excrementitious matter of the one, which, to the incu- 

 rious and uninformed, may appear ofi^ensive, and a pollution, is 

 perfectly fitted to contribute to the growth of the plant, 

 and its beauty. In harmony with this, is another fact, one 

 which I have lately ascertained, viz., that where there is no 

 rain, and, consequently, where there can be no vegetation, 

 there the lithate of ammonia, constituting the greater propor- 

 tion of the urine of birds, is converted, by the action of the 

 sun's rays, into a non-volatile but soluble salt, the perdurable 

 oxalate of ammonia — one of the principal ingredients of the 

 great depots of American and African guano — instances of 

 the most concentrated manure, hoarded in absolutely desert 

 wastes, forming a genuine sinking fund for the agriculture of 

 a country such as ours, wasteful of its natural manures. 

 The Oaks, Ambleside, August 31. 1844. 



We are informed by our friend David Stevenson, Esq., Civil Engineer, 

 tliat the deposit of guano on the Little Pentland Skerries, as mentioned 

 by Dr Davy, is about 30 yards in length, 20 yards in breadth, and 1 foot 

 in thickness ; and that the amount of this manure on that spot alone is, 

 therefore, probably about 200 yards, on about the same number of tons. 

 We would recommend the proprietors of the coasts and ishmds of the 

 north of Scotland to direct their attention to this subject. ~Edi tor. 



