806 



SIGNAL SERVICE. 



and knowing the present and antecedent rain- 

 fall higher up the river- valley, the office is thus 

 enabled to calculate and announce the time and 

 degree of coming changes. Thus timely pre- 

 monitions of the great flood-waves that pass 

 down the Mississippi, and also its fluctuations, 

 are issued from the office to the places which it 

 reached on its southerly way. 



The gauge used is very simple. It is a plank 

 (A, Fig. 2) of pine or oak timber, two inches 

 thick, ten inches wide, and long enough, when 

 placed obliquely on the slope of the river- 

 bank, to cover the extreme low-water and 

 high-water marks. When firmly imbedded in 



FIG. 1 



Extreme High Water. 



SIGNAL SERVICE RIVER-GAUGE. 



the earth, the mean level of the river or " bench- 

 mark " is marked on it as zero, and it is care- 

 fully graduated in feet and inches by means of 

 an upright measuring-rod (B), a straight-edge 

 and spirit-level crosswise, as shown by the 

 dotted lines (0) in the cut, each foot and its 

 subdivisions exactly corresponding to the ver- 

 tical foot and subdivisions of which they are 

 intended to be indices. A "danger-line" is 

 marked on the gauge, showing how tar the 

 water may rise, but no farther, without dan- 

 ger of a flood. The reports telegraphed to 

 the press, stating how near each stream has 

 risen to or fallen below the "danger-line," 

 enable the public to predetermine dangerous 

 inundations, and furnish steamboat-men and 

 merchants the daily information requisite for 

 intelligently directing the movements of their 

 craft. During the flood - months the tele- 



graphic river-reports are especially valuable to 

 all river-shipping, and to all interested in the 

 traveling and transportation facilities which 

 depend upon it, as well as giving timely warn- 

 ings of ice floods or sudden rises and falls. 

 The levee systems of the Mississippi and other 

 great rivers can thus be guarded, and the im- 

 mense agricultural interests secured, as the 

 flood-warning comes in time to summon the 

 State force to strengthen the imperiled works. 

 Daily bulletins of the river-reports are regu- 

 larly displayed at Augusta (Ga.), Cairo, Chatta- 

 nooga, Cincinnati, Davenport, Dubuque, and 

 Keok.uk (Iowa), La Crosse (Wis.j, Leaven- 

 worth, Louisville, Memphis, Morgantown (W. 

 Va.), Nashville, New Orleans, Omaha, Pitts- 

 burgh, Portland (Oregon), Eed Bluff (Cal.), 

 Shreveport, St. Louis, St. Paul, Umatilla (Ore- 

 gon), Yicksburg, and Yankton (D. T.). 



In connection with this service, surface and 

 bottom water-temperatures at points upon the 

 rivers, lakes, and seacoasts are observed and 

 reported for the United States Commissioner 

 of Fish and Fisheries, with a view to ascertain 

 the proper waters in which to plant the various 

 food-fishes and iurnish statistics desired for the 

 development of the national system of piscicul- 

 ture. 



There is also to be mentioned the oversight 

 given by the office to the changes of tempera- 

 ture by which the canals are closed by freezing, 

 or opened by thaws for transportation. During 

 the months when the market-rates and freight- 

 schedules are affected by the probabilities of 

 the canals closing, and when these waterways 

 are thronged with hundreds of laden barges, 

 the daily predictions indicate the thermometric 

 conditions likely to ensue along their lines of 

 transit. Such information may often protect 

 the public from the imposition of excessive 

 railway-rates in the shipment of the grain- 

 crops, especially in any autumn season of pro- 

 tracted mildness, and effect a large saving to 

 the mercantile world. 



2'he Cautionary /Storm-Signals, which ac- 

 company the " Synopsis and Indications " is- 

 sued to the press three times each day, con- 

 stitute a very important part of the Signal 

 Service work; and it was the possibility of 

 preparing such storm-warnings for the bene- 

 fit of navigation that originally gave the chief 

 stimulus to the establishment of a Weather 

 Bureau. The United States has a double front 

 with over 7,000 miles of sea-beaten coast, ex- 

 clusive of the shore-line of its great lakes, rav- 

 aged by terrific tempests ; and this vast stretch 

 of marginal territory needs to be environed 

 with stations from which observations can be 

 taken, and premonitory intelligence of cyclone 

 and anticyclone signaled by day and by night 

 to storm-ncenaced shipping. If no other duty 

 devolved upon the Service, this alone would 

 more than justify its whole cost, and warrant 

 its extension. It is one of the most difficult 

 and responsible tasks which can fall to the 

 meteorologist, to put his science to its utmost 



