It's right there in Clauses 5, Section 8, Article I of the Constitution: "The Congress shall have the power to fix the standard of weights and measures."

Yet Congress in the Republic's first 199 years was disposed to allow weights and measures common at the time of the Revolution to evolve into the hodgepodge now in use.

No more. In 1975, Congress passed and President Ford signed the Metric Conversion Act, designed to bring the United States in line with the rest of the world.

There was little rhyme or reason in the English system of weights and measures inherited from our ancestors and since abandoned by the British.

A yard was defined as the distance from the end of a man's nose to the tip of his thumb. An inch was three barleycorns, whatever they may be, laid end to end.

A rod, a measurement frequently spared nowadays, was the combined length of the left feet of 16 men standing in line, or 5 1/2 yards (why in the world would 16 men want to stand in line?)

A waterman knew a fathom (the distance between the fingertips of a man's outstretched arms) was 6 feet, not to be confused by horseplayers with a furlong, one-eight of a statue mile. An acre originally was the area of land a yoke of oxen could plow in a day.

Just to confuse matters even more, some English units of the same name are different in size. A pint is not the same in dry as in liquid measure; a troy ounce, used to weigh gold and other precious, metals, is lighter than an avoirdupois ounce, which is used to weigh equally rare filet mignon.

Never mind. The system, crazy as it may be, is ours and, if the polls are to be believed, we loved it (Gallup in November reported nearly 2-to-1 opposition to going metric).

Nevertheless, there has been some movement toward the metric system in the business world. The American drug, optical and Photographic industries went metric some years ago, and the automotive industry is fact following suit.

All wine is sold in the United States will be measured metrically by Jan. 1, 1979, and hard liquor will follow exactly a year later. Tipplers suspect they will not benefit from conversion. Some stores in the Washington area have been selling 1-5-liter jugs of wine at the same price as half-gallons (there are 3.8 liters in a gallon).

But pockets of resistance are forming across the land to flight what is seen as yet another unwanted federal intrusion into our private lives.

A bill has been introduced in the Indiana State Legislature to compel a Hoosier referendum before any switch to metric is made; a similar move is contemplated in West Virginia.

When the Federal Highway Administration last year announced plans to spend $100 million converting miles to kilometers on road signs, 5,000 letters poured in, 98 per cent of them opposed to the scheme, which was quickly dropped.

What the 1975 act provides for is establisment of a 17-member national Metric Board charge with coordinating "the voluntary conversion to the metric system."

There is no time limit (a 10-year limit proposed by the Senate was shot down in the House in the face of resistance from organized labor, which fears conversion will cost jobs), and the board has no enforcement authority. President Carter has appointed 16 members to the board, but none as yet has been approved by the Senate.

There clearly are advantages in going metric for the big multinational corporations that wheel and deal abroad. But for the rest of us, who needs it?

Will a woman be more shapely if her measurements are a Junoesque 91-60-91 (centimeters) rather than the classic 36-24-36 (inches)? Will a 2.27-kilogram box of chocolates say the same thing to one's maiden aunt as the more traditional 5-pound box? Will our land be more fertile when measured in hectares rather that permit them to drive 88.5 kilometers rather than 55 miles per hour? Will football addicts be prepared to accept first-and-nine (meters) rather than first-and-ten (yards)? Will cakes taste better when recipes call for 15-milliliter dabs rather than tablespoon?

When the weatherman tells us it's over 98 degrees Fahrenheit in the shade, we know dog days are upon us. But 37 degrees Celsius? It just doesn't sound right.

No, ladies and gentlement, it simply won't do. If we give the President's Metric Board a millimeter (.04 inches), it surely will take a kilometer (0.62 miles). Let the automotive, chemical, electrical and construction industries, which for their own reasons appear to favour the change, go their own way.

But let the average man not forget the immortal words of that homespun philosopher and sometime servant of the people, Bert Lance: "If it ain't broke, don't fix it."

Red-blooded Americans who would rather fight than switch will refuse to touch the metric system with a 3.048-meter (10-foot) pole.