In one letter he wrote to me, I find the following words: it never
occurred to me at the time that they were the gradual fruits of his
own experience on the subject:

"Physical and mental depression is a most fearful enemy. Other things
give you trouble at intervals—toothache, headache, etc., are all
spasmodic afflictions, and, moreover, can be much mitigated by
circumstances. But with depression it is not so: it poisons any
cup—it turns all the cheerful little daily duties of life into
miseries, unutterable burdens; death is the only future event which
you can contemplate with satisfaction. It admits of no comfort: the
whispered suggestion of the mind, 'You will be better soon,' falls on
deaf ears. No physical suffering that I have ever felt, and I have
not been without my share, is in the least comparable to it; the
agony of foreboding remorse and gloom with which it involves past,
present, and future—there is nothing like it. It is the valley of
the Shadow of Death.

"But when one first realizes how purely physical it is, it is an era.
I endured it for two years first: now I am prepared. I may even say
that though all sense of enjoyment dies under it, my friends, the
company I am in, generally suspect nothing."

This was literally the case. I knew his spirits were never very high;
but he seemed to me to maintain, what is far more valuable, a genial
equable flow of cheerfulness, such as one would give much to possess.

Among his occasional diversions at this time, I must place visiting
some of the worst houses in one of the worst quarters in London.