8 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Tears rolled ou, and the favorable opportunity wbicb I bad looked for to enable me to resume 

 my investigations of tbe pbenomena of storms did not come. Tbe Smitbsonian Institution bad 

 indeed organized a large body of meteorological observers, but most of tbe observers bad no 

 barometer, and many of tbe barometers wbicb were used were unreliable. At lengtb tbe Signal 

 Service was organized, and now came tbe opportunity for wbicb I bad been waiting tbirty years, 

 but bad almost despaired of living to witness. As soon as I had obtained one daily weatber map 

 for two years I commenced a careful examination of tbese maps, for tbe purpose of deducing from 

 tbem general laws. As tbe observations multiplied, I was enabled to undertake tbe investigation of 

 new questions, and tbe results are contained in a series of papers published in tbe American 

 Journal of Science, and entitled " Contributions to Meteorology." These papers have attracted 

 considerable attention in Europe. Tbe first nine papers were translated into French by M. Brocard^ 

 and were published in Paris bj^ tbe late Abb^ Moiguo, under the title of Meteorologie Dynamique 

 A very full abstract of several of these papers has been published in Italian by Dr. Ciro Ferrari, 

 of the meteorological oflflce at Home, in a pamphlet of 92 pages, with numerous plates. Notices 

 of most of tbe papers have from time to time appeared in various scientific journals of Great 

 Britain and the Continent of Europe. 



Tbe subjects investigated in these contributions were taken up without any regard to 

 systematic order, and the later results, having been derived from a much greater mass of materials, 

 will sometimes be found not to harmonize entirely with the results published in my earlier iiajXTS. 

 Under tbese circumstances it has been thought desirable to revise tbe entire series of papers, and 

 reduce them to a more systematic foim, improving the opportunity to combine new researches on 

 points heretofore neglected, and to deduce all results from the entire series of observations now 

 available, not only from the United States but from Europe and other parts of tbe world. Tbe 

 present memoir contains the first chapter of this revision, and it is designed that other chapters 

 shall follow as rapidly as my strength will permit. 



E. L. 



