BAROMETRIC PRESSURES ON THE GREAT LAKES 5 



daily mean elevations of the water surface and by the hourly elevations of 

 the water surface which have been mentioned. 



The above statement shows what data were fully used in the portion of the 

 investigation covered specifically by this publication. Many more data of 

 these kinds have been collected and used to furnish general checks on the 

 conclusions reached. For example, many more daily mean elevations of 

 water surface at various stations were collected and examined. So, too, the 

 barometric pressures have been secured and examined at eleven stations in 

 the vicinity of the Great Lakes for the two times named above on each day 

 in 28 months during the years 1909 to 1913, inclusive. 



Grateful acknowledgment is hereby extended to the two organizations 

 which have furnished the data used in this investigation and to several per- 

 sons in those organizations who have been especially helpful in supplying 

 information and valuable suggestions. 



The United States Weather Bureau has furnished all meteorological data 

 promptly or has given the opportunity to get it from the original records. 

 The Chief of the Weather Bureau, C. F. Marvin, has taken a continuous 

 interest in the investigation, has supplied many comments and suggestions, 

 and has given freely the benefit of his good judgment. Prof. Henry J. Cox, 

 meteorologist, in charge of the Weather Bureau station at Chicago, has 

 freely supplied working facilities during many days at various times for those 

 who have been working on this investigation. He and his assistants have 

 facilitated the work in many ways, but especially by granting free access to 

 the forecast maps and other records at the Chicago office. 



The United States Lake Survey (Survey of the Northern and Northwest- 

 ern Lakes) has furnished freely a large amount of information in regard to 

 hourly and mean daily elevations of the water surface at various gage sta- 

 tions on the Great Lakes, of which that used in the particular investigation 

 treated in this publication is but a part. 



Acknowledgment is hereby made to the various officers of the Corps of 

 Engineers of the United States Army who have been in charge of the Lake 

 Survey at the various times when data have been requested and furnished. 

 Especial acknowledgment is also extended to Mr. F. G. Ray and to Mr. 

 Thomas Russell, of the Lake Survey, for information given and courtesies 

 extended at various times in connection with this investigation. Mr. 

 Walter J. Graves, formerly of the Lake Survey, also furnished especially 

 valuable information and suggestions early in the investigation. 



Mr. J. A. Folse worked on this investigation as a computer for 4,000 hours 

 in all, intermittently, with many interruptions in 1913-20, and continuously 

 from June 1920 to July 1921, inclusive. In 1920 and 1921 all phases of the 

 investigation were discussed fully with him, and he has incidentally given 

 many valuable suggestions. The extensive use of plotted data, studied in 

 the graphic form, to supplement the analyses made by the least-square 

 method of computation, has been due largely to his insistent suggestions. 

 Such use has proved to be very effective in leading to a true understanding 

 of certain phases of the investigation. 



