Literature and law are eminently represented on two new regular issues in the Great Americans Series: a 14-cent stamp for the first American to win a Nobel Prize for literature and a 39-cent stamp for a man who helped America mobilize for two wars, yet was an ardent striver for world peace.

The 39-cent stamp, coming out Wednesday in Hanover, N.H., recognizes the largely unsung contributions of Grenville Clarke. The second stamp is a tribute to Sinclair Lewis and is being issued at his birthplace, Sauk Centre, Minn., Thursday.

The 39-cent rate applies to letters between one and two ounces and airmail to some Latin countries and most of the Pacific. The 14-cent stamp meets the new rate for post cards.

Sinclair Lewis (1885-1951) went at 18 from his small town to Yale, where he was a brilliant misfit in an orthodox university. In the next 13 years of writing and various publishing jobs, he showed no more promise than a gift for clever journalism that brought substantial checks from the Saturday Evening Post, Redbook and other magazines.

But in 1920 came "Main Street," which astonished, where it didn't outrage, reading America. It was followed in the next 10 years by four more of his greatest satires of the values and way of life of middle-class Americans -- "Babbitt," "Arrowsmith," "Elmer Gantry" and "Dodsworth." The books sold in the millions and made him the foremost American novelist of the decade.

"Babbitt," regarded by many as his most memorable book, focused on the confining, sterile life of go-getting businessman, solid citizen and club joiner George F. Babbitt. The book was greeted as one of the most incisive social commentaries written in English, and the title contributed a new word to the language.

"Arrowsmith" portrayed a young doctor whose ideals are pitted against the values of the medical profession. The idealistic aspects of "Arrowsmith" were an important factor in Lewis' winning the Nobel Prize in 1930. Earlier, "Arrowsmith" had brought him a Pulitzer Prize, which he turned down because of the earlier criticisms of "Main Street" and "Babbitt."

Grenville Clark (1882-1967), a Harvard graduate, prestigious lawyer and impeccable Brahmin, served his country in two wars and in the postwar search for peace, but always as a private citizen. "He was that rare thing in America," Supreme Court Justice Felix Frankfurter once said of him, "a man of independence, financially and politically, who devoted himself as hard to public affairs as a private citizen as he would were he in public office."

In World War I, in which he served as an officer, Clark recognized that the United States would eventually have to aid the Allies. He developed and ran the officer training (Plattsburg) plan under which qualified volunteers received the training that provided a pool of officers in the war.

In 1940, although America had begun industrial mobilization, there was no plan for mobilizing fighting men. Clark drafted what came to be known as the Selective Service Act, which was enacted over stiff opposition in September of that year, some 15 months before Pearl Harbor.

After World War II, Clark turned to establishing the rule of law -- instead of the rule of war -- to settle conflicts between nations. In 1958, his landmark book, "World Peace Through World Law," was published, laying down his proposals for international accord. His ideals continue to be pursued through the Grenville Clark Fund at Dartmouth, the first-day site.

The two stamps have been produced by intaglio, the Clark in purple, the Lewis in gray, in post office panes of 100 with a single-digit plate number.

Collectors of first-day covers have the usual alternatives with deadlines of April 19 for Clark and April 20 for Lewis.

Collectors affixing stamps: For the Clark issue, covers, which must bear addresses, should be sent to Customer-Affixed Envelopes, Postmaster, Hanover, N.H. 03755-9991. For the Lewis stamp, collectors must affix an additional 8 cents postage to meet the 22-cent rate. Covers should be sent to Customer-Affixed Envelopes, Postmaster, Sauk Centre, Minn. 56378-9991.

Postal Service affixing stamps: Collectors wishing the Clark stamp should send addressed envelopes to Grenville Clark Stamp, Postmaster, Hanover, N.H. 03755-9992. The cost is 39 cents per stamp affixed on a cover. For the Lewis stamp, the USPS will affix a Lewis stamp and two 4-cent Stagecoach stamps to meet the first-class rate. The cost is 22 cents per cover. Covers should be sent to Customer-Affixed Envelopes, Postmaster, Sauk Centre, Minn. 56378-9992.

Personal checks are accepted, cash is unwelcome, payment by postage stamps is rejected.