pleasant, reposeful hour after dinner when it was our custom
to sit in our respective easy chairs and, as we smoked our pipes,
discuss some of the many topics in which we had a common interest. The
postman had just discharged into the capacious letter-box an avalanche
of letters and circulars, and as I sat glancing through the solitary
letter that had fallen to my share, I looked from time to time at
Thorndyke and noticed, as I had often done before, with some surprise, a
curious habit that he had of turning over and closely scrutinising every
letter and package before he opened it.

"I observe, Thorndyke," I now ventured to remark, "that you always
examine the outside of a letter before looking at the inside. I have
seen other people do the same, and it has always appeared to me a
singularly foolish proceeding. Why speculate over an unopened letter
when a glance at the contents will tell you all there is to know?"

"You are perfectly right," he answered, "if the object of the inspection
is to discover who is the sender of the letter. But that is not my
object. In my case the habit is one that has been deliberately
cultivated--not in reference to letters only, but to everything that
comes into my hands--the habit of allowing nothing to pass without a
certain amount of conscious attention. The observant man is, in reality,
the attentive man, and the so-called power of observation is simply the
capacity for continuous attention. As a matter of fact, I have found in
practice, that the habit is a useful one even in reference to letters;
more than once I have gleaned a hint from the outside of a letter that
has proved valuable when applied to the contents. Here, for instance, is
a letter which has been opened after being fastened up--apparently by
the aid of steam. The envelope is soiled and rubbed, and smells faintly
of stale tobacco, and has evidently been carried in a pocket along with
a well-used pipe. Why should it have been opened? On reading it I
perceive that it should have reached me two days ago, and that the date
has been skilfully altered from the thirteenth to the fifteenth. The
inference is that my correspondent has a highly untrustworthy clerk."

"But the correspondent may have carried the letter in his own pocket," I
objected.

"Hardly," replied Thorndyke. "He would not have troubled to steam his
own letter open and close it again; he would have cut the envelope and
addressed a fresh one. This the clerk co