14 AVIFAUNA COLUMBIANA. 



Kosslyn. Just below the bridge is Analostan Island, which lies oppo- 

 site the shipping wharves of Georgetown for nearly their whole extent, 

 about half a mile. The island has a width of about 300 yards, and is 

 now used as summer resort and picnic ground. It is separated from 

 the Virginia shore by what is called "Little River," but which was for- 

 merly the main channel of the Potomac. Some thirty-five or forty years 

 ago a causeway was built across this channel to the Virginia shore, 

 thus cutting off the flow of water in this direction and forcing the cur- 

 rent around in front of Georgetown. This little dam joining Analostan 

 Island to the main-land proved, in the history of subsequent events, to 

 have been a cause of very great mischief to the Washington river front. 

 It was and is a great advantage to the shipping interest of Georgetown 

 by forcing the main channel down in front of the wharves. In an orni- 

 thological sense, it is of interest as having been instrumental — in con- 

 nection with the causeway in the middle of the river at the " Long 

 Bridge" — in developing immense tide- water marshes of wild rice (Zizania 

 aquatica). 



The Long Bridge is one mile and a quarter long and crosses the river 

 in front of the city of Washington at the foot of Fourteenth street. Be- 

 tween the Washington and Virginia channels of the river the bridge con- 

 sists of half a mile of earth causeway, impeding to this extent the current 

 of the river. The distance between the lower end of Analostan Island 

 and the Long Bridge is about one mile and a half, the river widening 

 from half a mile to a mile and a quarter. When the main current ot 

 the river swept through the channel behind Analostan Island it was 

 deflected at its lower end towards the east, and a large proportion of 

 the water was carried across to the Washington side, making a channel 

 along the entire Washington front of sufficient depth for vessels of light 

 draft. (See map of Potomac Eiver region.) 



A glance at the map will show the effect of closing this channel and 

 diverting the current to the north side above the island. When it 

 reaches the lower end of the island the entire current enters the Vir- 

 ginia channel, and the Washington channel is as effectually barred as 

 though dammed. Immediately the spaces marked by the dotted lines 

 began to fill up from alluvial deposits, and now they are marshes of 

 wild rice, marsh grass, wanquapins, etc., which afford feeding grounds 

 for vast numbers of Reed-birds (Dolichonyx oryzivorus), Rail (Porzana 

 Carolina audEallus virginianns). Blackbirds (Agelwus pliceniceus), Marsh 

 Wrens (Cistothorns palustris), etc. 



We have referred more in detail to the formation of these marshes 

 than we otherwise would because they have another and more impor- 

 tant significance than the ornithological one — one which, although not 

 connected directly with the subject of this paper, still is of sufficient 

 general interest to deserve a passing notice. We refer to the increased 

 production of malarial diseases in the adjacent portion of Washington 

 City as a result of these marshes. The subject has also an indirect in- 



