August, '13] BUTTRICK: TIDES AND MOSQUITOES 357 



tide was predicted, as will be seen from the curve, as 6.8 feet. This 

 is sufficient to flood the West River Marshes. Development in ordi- 

 nary August weather generally takes about one week; hence oiling, 

 to be successful, must be done before the following Saturday night, 

 or August 17. It will also be seen that the tides would continue to 

 flood the marsh at least once daily till the end of the week so that 

 oiling would have to be carried on with the tide still on the marsh. 



Some idea of the accuracy of the predictions is obtained by com- 

 paring the predicted curves with actual tide gage readings plotted on 

 the same sheet in the accompanying figure. Gage readings were 

 obtained from Engineer Corps, U. S. Army, and were taken from tide 

 gages in New Haven and Bridgeport harbors. The 1912 readings 

 were taken from a gage in Bridgeport Harbor and correction factor 

 figured mathematically. This probably accounts for some of the dis- 

 crepancies. It will be seen that they are of sufficient accuracy to 

 afford a reliable basis for planning an oiling campaign and if checked 

 by gage readings from day to day would be of still greater value. 



A given curve shows the periods of maximum high tides for an ex- 

 tended region, probably for all points within the same time belt, 

 and would thus give a rough idea of the number of broods of mos- 

 quitoes to be expected in a given season over that territory; but for 

 the actual heights and times of floodings a curve has only a local value. 

 The territory over which it could be used for these purposes depending 

 on the configuration of the coast line which determines the time and 

 height of the tides locally. Thus, an open coast line which the tide 

 wave strikes at right angles will have high water at approximately 

 the same time for long stretches and it will rise to approximately the 

 same height. On a broken coast line with bays, estuaries, fiords, etc., 

 where the tide wave runs parallel to the shore, the time and height 

 will vary greatly. At New Haven, where the tide wave runs parallel 

 to the shore, a single curve only was used, but it is probable that 

 better results would have been obtained if a separate one had been 

 used for some of the outlying marshes. And it is certain that if the 

 campaign had included Branford and Milford, points 10 miles east 

 and west of New Haven harbor, respectively, that at least three 

 curves would have been required. 



The predictions are usually given for a certain point, a wharf head, 

 breakwater, lighthouse, or the like. The salt marsh may be some 

 miles away. If further up harbor, an addition sometimes as great 

 as 2 hours must be made for the tide to reach that point. If down 

 harbor, it does not necessarily follow that a deduction is required, 

 as the resistance of the stream bed and marsh surface to the tide wave 

 is great and even here the tide is apt to be at flood later than at the 



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