208 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946: 
between the fluorine content of the waters and the water-bearing 
layers from which they are derived. 
This paper is a presentation, not of final conclusions, but rather of 
the methods of research used and of some of the problems met with 
in carrying on the study, and of the results reached so far. 
COLLECTING THE DATA 
The first step in collecting data on fluorine in the water supplies 
of the United States was the sending of a form letter to the Sanitary 
Engineer of each of the 48 States and of the District of Columbia. 
With the aid of a reprint from the Geographical Review ® the plans 
for an Atlas of Diseases were presented, and information was re- 
quested on the presence of fluorine in the waters of the State, on lit- 
erature dealing with the matter, and on agencies from which further 
information might be obtained. 
Within a reasonably short time replies had been received from all 
but two States. A few of these replies merely stated that no data 
were available. Most of them, however, furnished concrete informa- 
tion, sometimes much, sometimes little, but always helpful. This in- 
cluded material of the following types: 
1. Tabulations of statistics, both published and unpublished. 
2. Reprints and maps. 
8. References to publications. 
4. Names of individuals, firms, and public agencies from which additional 
information might be obtained. 
5. Personal statements, some detailed, some general, about the presence or 
absence of fluorine in the water supplies of the State. 
For half a dozen States the answer was that data such as we wanted 
were in process of tabulation and would be sent as soon as available. 
Some of this material has not yet been received. 
Letters were then written to all persons and agencies referred to in 
the answers to the first form letter. These brought similar types of 
replies. 
The enthusiastic responses from the sanitary engineers to whom 
we first wrote and from the health officers, State geologists, and others 
to whom they referred us are deeply appreciated. Many of these men 
went to considerable trouble to assemble statistics and compile maps 
for our use. Some of them have written more than once, and prac- 
tically all have expressed interest in the project and a desire to help 
in any further way possible. Without such wholehearted cooperation 
it would have been impossible to accomplish as much as has been done. 
The next step was, of course, a study of the literature on the subject, 
the references being acquired from the above correspondence, from in- 
dexes, and from cross references. 
* Op. cit. (see footnote 4). 
