SOUTH SHORE OF THE MAINLAND 103 



retaining this color for days. Drew has found in 

 tropical waters denitrifying bacteria that in their 

 life economy transform certain soluble calcium 

 salts to the insoluble calcium carbonates, precipi- 

 tating the latter in the form of minute granules. 

 These bacteria are especially abundant in the 

 Bahaman and South Floridian waters. This is 

 partially the cause of much of the milldness of the 

 water of this region and accounts for the origin of 

 the soft oolitic mud found throughout Hawk Chan- 

 nel and all our shallow bays. Year in and year out 

 these bacteria are changing a part of the liquid sea 

 water into a solid which is being added to the land; 

 All the hammocks along the south shore have this 

 marl for a foundation; their upper soil being only a 

 thin layer of mold. It is refreshing to find a new 

 bacteria that does good instead of evil. 



Several years ago I visited Flamingo in No- 

 vember for the purpose of making natural history 

 collections. The edge of a hurricane had passed 

 over the region shortly before and, with the excep- 

 tion of the higher hammocks, the country was 

 covered with water, — in places to the depth of 

 two feet. We had several partly cloudy, showery 

 days and the mosquitoes swarmed everywhere to 



