34 CHEMICAL MANUEES. 



Soft PhospJiate of Palk County. — Water 835 per cent ; phos- 

 phoric acid, total 28 '9 per cent, of which 0'87 per cent is soluble 

 in citrate (Wagner's method) and 2'05 soluble in citrate (Peter- 

 mann's naethod) ; 2'83 per cent of oxide of iron, and 0*86 per cent 

 of clay. 



Soft Phosphate of Alafia Creek. — Water 5*8 per cent ; phosphoric 

 acid, total 9*4 per cent, of which 0*62 per cent is soluble in water; 

 oxide of iron 7 '5 per cent ; clay 10'26 per cent. This quality of 

 phosphate is used directly as manure, being simply ground fine. 



River Pebbles are found in several rivers of the west part of 

 Florida, chiefly in Peace Eiver and Alabama Eiver, where they 

 sometimes form considerable deposits. This phosphate can be 

 extracted cheaper than all others. Powerful dredges fitted with 

 centrifugal pumps lift the sand and pebbles ; these are afterwards 

 separated from the sand by a slightly inclined rotary sieve consist- 

 ing of iron rods. The sand passes through the meshes, and returns 

 with the water into the river, whilst the phosphate issues from the 

 sieve at the lower extremity, mixed with stones and pieces of wood. 

 It is taken to the dryer without further cleaning. The daily yield 

 of a dredge varies according to the quality of the material lifted 

 by the pump. Thus on certain points of the river the phosphate 

 is very pure, whilst on others nothing but sand is found. Some 

 days 100 tons of phosphate are collected, other days only 20 tons. 

 The installations at work on Peace Eiver produce on an average 

 -50 tons of phosphate per day. The cost of extraction of river 

 pebbles is in general not heavy; however, the cost price per ton 

 exceeds a dollar on an average. The waters of Peace Eiver in- 

 cessantly bring phosphates to certain points, and remove it from 

 others. Whatever may be the importance of the deposits of Peace 

 Eiver phosphates, they are not inexhaustible, and the time can be 

 seen when they will cease to be workable. Eiver pebbles are in the 

 form of nodules, the size of which varies from sand grains to nuts. 

 The corners are rounded, and the surface is often polished and 

 brilliant. The colour is dark-grey, blue, or black. The land pebbles, 

 from which the river pebbles are formed by washing, are generally 

 pale, and it is believed that the black colour of the river pebbles 

 comes from the tannin of the plants which grow on the banks of 

 the rivers. Analysis reveals no difference between the two phos- 

 phates. Both have the same composition, 65 to 70 per cent of 

 phosphate of lime, with less than 3 per cent of oxide of iron and 

 alumina. However, the impurities found mixed with river pebbles 

 have the effect of bringing the phosphates of lime down to from 

 60 to 65 per cent. 



Land Pebbles. — All the country, between Peace Eiver and 

 Alafia Eiver, in the counties of Polk, Hilsborough, de Soto, Manatee, 

 contain phosphate deposits. The richest region is a strip of land 



