A GENIUS IN THE FAMILY; By Hiram P. Maxim (1936).

IN 1935, to rapturous cries from the reviewers, Clarence Day published a book about his 19th-century childhood. He called it Life With Father. Father was a self-confident, pre-Freudian New Yorker -- a rich stockbroker utterly untroubled by doubts of any sort. To be part of his household was sort of like living with an affectionate steamroller. To be his eldest son was to have the steamroller always start on your patch of street. Day made the most of this situation, combining insight and high comedy. The public loved it.

Success breeds followers. The next year another book about a steamroller childhood came out. This one was called A Genius in the Family. Once again the author was the eldest son, and once again the star was a self-confident, pre-Freudian father, this one named Hiram Maxim. (Later he became Sir Hiram, when he got mad at the U.S. government and moved to England.)

Who needs two books about dominant WASP fathers in late 19th-century New York? Well, as it happens, anyone who enjoys good reading does. Hiram Maxim Jr. doesn't write nearly as well as Clarence Day Jr., but he has the same total recall of his childhood. He has as keen a sense of the ridiculous -- and he has even richer material to work with. Father Day was a normal Victorian writ large: a well-bred New Yorker in a tall silk hat, self-assured enough to allow his eccentricities free play, but underneath made of the same kind of flesh as the rest of us.

Father Maxim, though he, too, wore a tall silk hat, and must have looked quite similar when he walked down the street in Brooklyn, differed a lot from most people. To begin with, he really was a genius, and one of the more picturesque varieties. He was a mad- genius inventor. He made a fortune with the Maxim machine gun, almost beat Edison to the electric light, spent much of the 1890s building steam-powered airplanes. These matters concerned him; most aspects of everyday life did not. Even more than Mr. Day, Mr. Maxim was unself-conscious about his behavior.

For example, in the very respectable part of Brooklyn where he and his family lived, it was customary to have a tiny lawn in front of your house. To protect the grass, you put up a heavy cast-iron fence with a heavy cast- iron gate in it. This you had to pull open and swing shut every time you went in or out. Only not Mr. Maxim. He was always in a hurry. And in his top hat and Prince Albert coat he would vault over the gate.

What really set him apart, though, were his persistence and his odd, almost inhuman sense of humor. As to persistence, how many people, after being robbed of a bag of gold in Paris, would routinely scan crowds ever after, just in case they might spot one of the robbers? Or having spotted one in London, 13 years later, would compel a couple of Scotland Yard detectives to join them in a stake-out, and keep the poor men there two full days? Or having got the robber arrested and extradited, would drop all other business and spend a month in France making sure he got convicted?

Father Maxim was prepared to put that kind of effort into almost anything, including his jokes. Take the case of the counterfeit penny. When little Hiram was about 4, he conceived a passion for a small white dog owned by the neighborhood druggist. One day he got carried away and asked if the druggist would give him the dog. What he got was a wise-guy city answer. Sure, sonny, bring me a two-headed penny and I'll give you the dog.

At least in 1873, 4-year-olds were naive. Little Hiram hurried home and asked his mother to check her pennies, in case she had a two-headed one. They don't exist, she told him. But trusting the druggist, he wouldn't believe her. When his father got home, same question but different response. Father Maxim goes through all his pennies twice, seems surprised that none has two heads, says there are sure to be two-headed ones over in Manhattan. He'll look tomorrow.

What he actually does the next day is to suspend his research for the United States Electric Light Company and spend the morning making one. That night he pretends to have forgotten the whole thing, and is startled when little Hiram finds a two-header in his pocket. (The druggist is dumbfounded when he sees it, but does not yield the dog.)

THAT JOKE was kindly. So, more or less, was the one where Father Maxim assures his young son that the barren peach tree in the back yard will yield a bountiful and quite speedy crop if fertilized with a dead cat. (Dead cat? Street cleaning was not elaborate in the 1870s, and with a little looking a boy could expect to find almost anything somewhere in the neighborhood.)

But the hot poker trick was not kindly. Like many prosperous New York families in the 1870s, the Maxims had an Irish cook. It amused Father Maxim to test the claim he had read that extreme heat and extreme cold feel the same to human touch. The cook was completely taken in, fainted, and, as soon as she recovered consciousness and some degree of coherence, quit, "declaring she would not remain with a family where the man of the house branded the servants on their necks." (Of course there was no brand.)

As his son tells the story, Sir Hiram was not conscious of the cruelty involved. He just had an original mind and a complete willingness to use people experimentally. Hard on the cook in that case, wonderful for his daughter Florence in another case. When little Florence first encountered arithmetic in school, she couldn't seem to grasp it. After some weeks, her teacher announced that she was mentally retarded and never would grasp it. That same evening her indignant father invented a new way to teach arithmetic, tried it out on his daughter, discovered he could teach her more in one evening than her class had learned all fall. She never had trouble with math again.

Hiram Maxim was a true original. Hiram Jr. was not a true writer -- he preferred designing automobiles and gun silencers -- but he rose to his subject. A Genius in the Family is worth a few rapturous cries.