Dear Mr. Nelson:
It has been some weeks since you made the new lead-screw for our high resolution interferometer. I have delayed writing to you until we had completed all of the remaining parts necessary for testing the overall instrument's operation in its improved configuration. We have come far enough now to be able to report to you that the new lead-screw performs superbly. With the combined screw and integrating nut, we are unable to detect any variation in the reference laser fringe rate caused by the screw itself.
This is a very impressive result, which attests directly to the high quality of your work. Needless to say, we are delighted. Thank you very much for your help in this endeavor and, not the least, for your very prompt response to our request.
C. B. Farmer
Earth and Space Sciences Division