Advancing years did little toward destroying Mark Twain’s interest in human affairs.  At no time in his life was he more variously concerned and employed than in his sixty-seventh year—­matters social, literary, political, religious, financial, scientific.  He was always alive, young, actively cultivating or devising interests—­valuable and otherwise, though never less than important to him.

He had plenty of money again, for one thing, and he liked to find dazzlingly new ways for investing it.  As in the old days, he was always putting “twenty-five or forty thousand dollars,” as he said, into something that promised multiplied returns.  Howells tells how he found him looking wonderfully well, and when he asked the name of his elixir he learned that it was plasmon.

I did not immediately understand that plasmon was one of the investments which he had made from “the substance of things hoped for,” and in the destiny of a disastrous disappointment.  But after paying off the creditors of his late publishing firm he had to do something with his money, and it was not his fault if he did not make a fortune out of plasmon.

It was just at this period (the beginning of 1902) that he was promoting with his capital and enthusiasm the plasmon interests in America, investing in it one of the “usual amounts,” promising to make Howells over again body and soul with the life-giving albuminate.  Once he wrote him explicit instructions: 

Yes—­take it as a medicine—­there is nothing better, nothing surer of desired results.  If you wish to be elaborate—­which isn’t necessary—­put a couple of heaping teaspoonfuls of the powder in an inch of milk & stir until it is a paste; put in some more milk and stir the paste to a thin gruel; then fill up the glass and drink.

    Or, stir it into your soup.

    Or, into your oatmeal.

    Or, use any method you like, so’s you get it down—­that is the only
    essential.

He put another “usual sum” about this time in a patent cash register which was acknowledged to be “a promise rather than a performance,” and remains so until this day.

He capitalized a patent spiral hat-pin, warranted to hold the hat on in any weather, and he had a number of the pins handsomely made to present to visitors of the sex naturally requiring that sort of adornment and protection.  It was a pretty and ingenious device and apparently effective enough, though it failed to secure his invested thousands.

He invested a lesser sum in shares of the Booklover’s Library, which was going to revolutionize the reading world, and which at least paid a few dividends.  Even the old Tennessee land will-o’-the-wisp-long since repudiated and forgotten—­when it appeared again in the form of a possible equity in some overlooked fragment, kindled a gentle interest, and was added to his list of ventures.