128 PROCEEDINGS OF THE [Dec, 1886. 



ved at any of these intermediate returns. It is a telescopic Comet, witli peri- 

 helion distance greater than the Earth's mean distance from the Sun by at least 

 l-7th ; it is barely visible to the unaided eye when nearest the Earth, and can 

 be best observed when it comes to its perihelion about the middle of September. 

 If it comes to its perihelion a couple of months before or after this date, it will 

 less easily be observed. 



The po^raboUc orbit of Comet 1886&, is inserted in the Table, as I have seen 

 no notice of any elliptic orbit yet calculated. The number of Nature for 

 2 1st Oct. contains none, and that for 28th Oct. has not yet reached me ; they 

 arrive frequently three or four weeks after date. 



DECEMBEK 23d, 188G. 

 The President in the Chair. 

 The following paper was read : 



On the probable source of the Phosphorus in the South Carolina 



Phosphates. 



BY G. E. MANIGUALT, M. D. 



The deposits of a rock known as Phosphate of Lime, an important ingredi- 

 ent, when ground to powder, of the commercial fertilizers which are largely 

 used at present in agriculture, occur over a wide range of country along the 

 seaboard of the South Atlantic, reaching from North Carolina to Florida. They 

 are confined mainly to the coast, but extend in a few instances to a distance of 

 sixty miles inland. The centre of the deposits is in South Carolina, between 

 the cities of Charleston and Beaufort, and it is there only that its mining is 

 profitable, as, out of that area, the rock is either not favorably situated for 

 economical handling, or does not contain a sijfficiently high percentage of 

 phosphate of lime to be advantageously worked. 



The question as to the source from whence came the phosphorus which uni- 

 ted with the lime to form this combination, has been a puzzling one. Several 

 theories have been advanced, which are as follows : The first, which originated 

 with the elder Prof. C. U. Shepard, assumes that the fragments of marl were 



