fuller] COLLECTION OF WELL RECORDS AND SAMPLES. 31 
be sent you, in order that the samples may be transmitted through the mails without 
the payment of postage. 
In some cases it is necessary that records be regarded as confidential, and in these 
cases the information will be carefully guarded and used only under the conditions 
which you stipulate. 
When the first letter inviting cooperation is sent out the date is 
entered on the card (p. 29). If a reply is not received in two weeks 
or a month, it is often desirable to send out a second letter. In order 
to keep track of this correspondence, projecting metal clips of differ- 
ent colors are used. Thus, if the first circular is sent out on January 
1, and it is desired to send a second letter on January 15, the date 
January 1 is entered on the line opposite "circulars sent," while the 
clip is placed on the number 15 at the top of the card. As the cards 
are of uniform size and fit closely into the drawer, all the clips for a 
given date fall in a single line, and it is easy to select the cards for a 
particular date without handling those relating to any other date. To 
assist still further in handling the correspondence, clips of the follow- 
ing colors are used for the different classes of cooperators: Copper 
for persons such as foremen for large firms saving samples by order 
of employers or others; white for all other persons saving samples; 
green for owners not saving samples, and steel-blue for drillers not 
saving samples. 
If a reply is not received to the first letter by the end of two weeks, 
a second letter is sent, which is commonly as follows: 
Second letter sent to drillers and well owners. 
Sir: In order that the collection of well samples being made by this office may be 
as complete as possible, one of the inclosed forms is sent at stated intervals to all 
persons interested in well drilling. 
If you will save samples of well borings for the Geological Survey, please fill out 
this card, which requires no postage, and return it to this office, when a supply of 
canvas bags, which will carry the samples through the mail without the payment 
of postage, will be sent you. 
The card should also be filled out if you need additional sample bags or if you are 
about to move your outfit to a new place. 
If a reply to the second letter is not received, the same form is sent 
again after an interval varying with the individual circumstances. 
By repetition the letter serves to impress the importance of the work 
upon persons not responding to the first invitation, with the result 
that cooperation is sometimes finally secured. The same letter is also 
sent from time to time to persons saving samples, in order to keep in 
touch with them, to make sure that the work is not forgotten, and 
that the necessary supplies are ordered as required. 
With the original letter inviting cooperation and with the second 
letter there are inclosed a sample of the bags used for shipping samples 
and a franked card on which the recipient can designate the number 
of notebooks and bags required. 
