300 UNITED ST A TES DA IL Y A TMOSPHERIC S UR VE Y 



tions, which by the aid of simultaneous measurements and the 

 electro-magnetic telegraph joining the places of observation by 

 a magic touch is presented to the trained eye of the forecaster. 

 Each twelve hours the kaleidoscope changes and a new graphic 

 picture of actual conditions is shown. Where else can the me- 

 teorologist find such opportunity to study storms and atmos- 

 pheric changes ? 



In the middle of the eighteenth century Franklin detected the 

 rotary and progressive motions of storms ; earl}'- in the nine- 

 teenth century Redfield and Espy contended over rival tlieories 

 as to the mechanical principle involved in the formation of storms, 

 and a little later Maury studied the storms of the Atlantic ocean ; 

 still later Loomis, Dove, and Ferrell reviewed these theories and 

 added much to our knowledge ; but at this late date no one has 

 been able to satisfactorily coordinate the forces operative in 

 cyclones or to assign quantitative values to the horizontal temper- 

 ature and pressure gradients, to the surface and internal frictions 

 of convection, to centrifugence, to the latent heat of condensation, 

 and to the effect of hemispherical circulation. Probably the only 

 component of cyclonic force that is well understood and accu- 

 rately computed is the deflection due to the earth's rotation. 



Our early investigators studied only the storms of low levels 

 and humid airs, where convection was only needed to carry the 

 moist air currents to but a slightly higher elevation before cool- 

 ing by expansion would produce condensation and an immediate 

 acceleration of the cyclone by the liberation of latent heat. They 

 had never seen the whirling cyclones of the arid northern Rocky 

 Mountain plateau dash down upon our Great Lakes with rapidly 

 increasing energy, notwithstanding the fact that there was little 

 or no condensation, and hence no addition of the latent heat 

 which'Esp}^ supposed was absolutely essential to a continuation 

 of storms. 



The widely differing elevation, topography, temperature, and 

 aridity of the broad region under observation give conditions 

 which are unequaled anywhere in the world for the advantages 

 which they present to the physicist to study the mechanical 

 phases of storm development and progression, or at least such as 

 can be profitably studied with observations taken only at the 

 bottom of the great aerial ocean surrounding the earth. 



Here we see summer cyclones formed under the intense inso- 

 lation which beats down through a diathermanous atmosphere 

 upon the arid waste of the Rocky Mountain plateau ; cyclones 



^ 



