146 MANURE. 



gress of deposit, by living birds, says that in three 

 centuries, the excrements of birds have added only 

 a few lines to the depth of the deposit. What 

 a length of time must have elapsed, or how incredi- 

 ble the number of birds, to have produced that pile 

 of guano, whose base, washed by the sea, was ob- 

 served by our countryman, Mr. Blake, to stretch a 

 mile in length, and to tower 800 to 900 feet high ! 

 The composition of guano, countenances the idea of 

 its being the excrements of birds ; probably they be- 

 longed to that ancient flock, whose huge foot-marks 

 have left their impress on the shores of an estuary, 

 which has since become the sandstone of the Con- 

 necticut river valley. 



212. The latest analysis of guano, is that of 

 Voelckel, and may be here cited. 



Urate of ammonia, 9* 



Oxalate of ammonia, 10-6 



Oxalate of lime, 7* 



Phosphate of ammonia, 6* 



Phosphates of ammonia and magnesia, 2-6 

 Sulphate of potash, 5-5 



Sulphate of soda, 3*8 



Muriate of ammonia, 4-2 



Phosphate of lime, 14*3 



Clay and sand, 4*7 



67-7 



