The Leonardo da Vinci manuscript bought last month in London for $5.2 million by Dr. Armand Hammer will go on public view tomorrow at the Corcoran Gallery of Art. Because the so-called "Cidex Leicester" is less an artist's sketchbook than a scientific treatise, it is more impressive as an autograph than as a work of art.

Its picutres are all tiny. Most are merely diagrams. It is true that Leonardo was the mightiest of masters, and any object from his hand may send shivers through the viewer. But unless you can read Renaissance Italian, and read it backwards, this is not an exhibition you should feel you must see.

Water and cosmology are the central subjects of the fact-crammed dialogues -- between Leonardo and imaginary adversaries -- that fill the "Codex Leicester." At Hammer's direction, its 18 large paper pages have been taken from their binding and sandwiched between plastic sheets so that both sides may be studied. On one of them two little men, each one-half-inch high, balance on a seesaw. They are the only human figures in the Corcoran's display.

Leonardo, in these pages, writes of many things -- siphons, evaporation, "how to empty a swamp that flows into the sea," the origin of rivers, distillation, "the color of the atmosphere" ("I say that the blueness we see in the atmosphere is not intrinsic color, but is caused by warm vapor . . . on which the solar rats fall"), dams, canals and rain. He even hints at steam engines and submarines. He writes of fossils found on mountain tops and "of the silliness and stupidity of those who will have it that these animals were carried up to places remoted from the sea by the Deluge." He was not always right. Leonardo thought the moon was clothed in water, and that it did not pull the tides.

"There is no work of art in the world I wanted more than this," Hammer said last December when he won the work at auction (for what was said by some to be a bargain-basement price). The 82-year-old multi-millionaire industrialist, who founded Occidental Oil, has long promised to bequeath his pictures to two American museums. His oils will eventually be placed in the wing that bears his name at the Los Angeles County Museum of Art. But he has said his master drawings -- he even owns a Leonardo -- are destined for the National Gallery of Art. John Walker, the Gallery's director, emeritus, has long been his adviser, and curators of drawings employed at that museum have served as Hammer's scouts. So there was reason to believe that his "Codex Leicester" would eventually come here.

It won't. Though the notebook is surely not a painting, "it's not a drawing either,"Hammer said yesterday. "The reason I'm giving it to L.A. is that I consider it a manuscript -- though, of course, I know that Carter Brown would love to have it."

Carlo Pedretti, whom Kenneth Clark describes as "unquestionably the greatest Leonardo scholar of our times," works at UCLA's Elmer Belt Library of Vinciania. It was he who advised Hammer that the notebook would be sold.

Pedretti contends that the Codex, titled "Of the Nature, Weight and Movement of Water," was compiled in 1507-08, and that much of it was copied by the master from other notebooks long since lost. "There are no corrections in it, and no second thoughts, but he never merely copied. He always elaborated as he went along. The word 'Codex,' by the way, is an inaccurate description," Pedritti said yesterday. "The term refers to a book already bound before the author writes on its blank pages. Leonardo, it is clear, wrote on both sides of these pages before they were bound."

Perhaps not surprisingly, Pedretti finds these yellowed pages awesomely important. "This is one of the greatest documents in the history of humanity, since Aristotle, say. Look at the handwriting. It's beautiful. It is Leonardo's in his own voice, as if he were on tape."

Other Leonardo notebooks, those in Italy and France and at Windsor Castle, contain drawings far more beautiful than those that may be seen in the Codex Leicester. "Much of the background of the Mona Lisa is buried, so to speak, in the pages of the Codex Leicester," says Pedretti. "But in the end one has to read them. It is now our duty to come out with a full English translation."

The Fine Arts Committee for the Presidential Inaugural is sponsoring the one-week exhibition. Five hundred numbered, hard-bound copies of the catalog that Christie's published when they auctioned off the notebook will be sold by the committee for $100 each. Though tickets are required for the Corcoran's exhibit, admission will be free. The show closes Jan. 25.