be necessary to see the envelope in which the letter came or, excepting in unusual circumstances, to refer back to previous correspondence to get at the facts essential to the answering of the letter in hand. The references to the subject under consideration should be accurate and full enough to require no further investigation or explanation. I have on my desk as I write these sentences a letter which I can by no possibility answer intelligently until I get further details. The writer's reference to the business under discussion is vague, and his previous correspondence, even when I have dug it out of the files, does not adequately disclose the significance of the matters to which he refers in his last letter. If one has only a very limited correspondence, then he may reasonably be expected to carry in mind most of the details of what has been previously said, but if his letters run from fifty to one hundred or five hundred a day and cover a wide range of topics the case is different. An illustration is before me.
"Your letter with reference to my son's scholastic record for the past semester is
