192 



study of the topo-graphic maps of this region shows that many 

 of the streams are sluggish and that lowi lands are frequently 

 overflowed. It is believed that this entire regioni is well suited 

 to the breeding of mosquitoes; the season is long, with warmi 

 weather and many warm; nights and an abundance of breeding 

 places. The number of cases of mialaria in Central Virginia is 

 probably influenced tO' some extent by the fact that there are a 

 great many colored people and some very poor white people 

 living in this region, for the malaria situation is aggravated in 

 some communities by unscreened houses and the shiftless habits 

 of the residents. 



We next consider the tidewater region; this is separated from, 

 Middle Virginia by the fact that the soil is derived from a 

 different geologic foTmation. The line separating these two 

 areas, roughly speaking, passes southwaird through Washington 

 and Richmond. This section is divided by the waters of the 

 Chesapeake Bay and the large tidal rivers that flow intO' it. This 

 is mainly an alluvial country, a portion of the tertiary Atlantic 

 Tidewater plain, and its surface, composed of sands and clays, 

 is thrown into low, flat ridges, forming the watershed of the 

 peninsulas, succeeded by terraces and plains down to the water's 

 edge, where they meet the swamps and salt marshes that ahvays 

 accompany well-developed, land-locked, tidal waters. It is esti- 

 mated that there are a million acres of swamp and periodically 

 overflowed land in Virginia, a large amount O'f wfnich is located 

 in the southeastern part of the State in the Dismal Swamp 

 region. Many of the rivers are in, reality a long marsh with a 

 small, winding stream running throuigh it, the stream^ overflow- 

 ing its banks after each heavy shower. This statement is true of 

 many of the streams in this region, and especially of these that 

 are in the region of the Dismal Swamp. The Virginia Penin- 

 sula or eastern shore is doubtless similar tO' the eastern portions 

 of Maryland and New Jersey, and, therefore, needs nO' further 

 description. The ocean side of the peninsula is a long stretch of 

 shallow bays and salt marsh 70 miles long and of varying width, 

 and is the breeding place of many mosquitoes ; the western side, 

 however, is very different and at points examined is almost 

 devoid of breeding places. 



