MINERAL INDUSTRIES LIME AND LIMEiTONE. 43 



dence the ocean waters were allowed once more to come in, the 

 marine shell marls being deposited during this time. The general 

 upward movement, however, continued, the whole area being 

 finally lifted to its present height of from lo to 20 feet above sea 

 level. 



This exposure at Fort Thompson affords the key to the study 

 of the formations extending to the east and underlying the Ever- 

 glades, in which the limestones and marls of this type are widely 

 distributed. In following up the canal from Fort Thompson these 

 limestones and marls are seen in the canal banks for a mile or so 

 where all except the upper freshwater marl drop below water 

 level. That they are still present, however, is shown by the quan- 

 tities of shells that have been thrown out by the dredge. At Coffee 

 Mill Hammock, about 8 miles above Fort Thompson, a slight fold 

 or anticline brings the rock to the surface, and for a few miles 

 the limestone and marl are again seen in place in the banks of the 

 canal. It is worthy of note also that at this locality the dredge 

 cuts entirely through the overlying deposits and brings up the Oa- 

 loosahatchee marl from beneath., showing the eastward extent of 

 that formation beyond the locality at which it disappears from 

 view in the river bank. Beyond the Coffee Mill Hammock cut. 

 limestone and marls are occasionally reached by the dredge. A 

 considerable mass of shells has been taken from the canal just 

 above Citrus Center Landing, while within three miles of Lake 

 Hicpochee a rather heavy limestone comes to the surface. 



Within Lake Okeechobee there is a reef of rock extending in a 

 general northwest-southeast direction between Observation and 

 Rita islands. At a point about 5 miles southeast of Observation 

 Island the rock of this reef now stands above water at intervals 

 for a mile or so, the maximum exposure at the present low water 

 stage being about two feet. At the surface this limestone is quite 

 hard, or is streaked in a characteristic manner with alternate hard 

 and soft layers. Beneath the surface, however, the rock is a rather 

 soft oolitic marl or limestone of granular texture and light yellow 

 color. The hard phase of this limestone is much like the lime- 

 stone found in the canal three miles west of Lake Hicpochee, while 

 a thin stratum of a similar limestone is found near the surface at 

 Coffee Mill Hammock. A few pieces of the marl phaSe of this 



