Morris Udall has fathered many necessary measures to advance the general welfare that the Constitution says is one of the only reasons for government to exist. And now, like a justifiably proud father of a large family, he is harshest in his criticism of a favorite for whom he had the highest hopes of immediate perfection: The Surface Mining Control and Reclamation Act of 1977.

The Arizona congressman's critique of the act on the 10th anniversary of its passage {op-ed, Aug. 12} fastened on the youngster's few faults to the virtual exclusion of its more numerous virtues and accomplishments. Much has happened since the act became effective in 1978:

A second oil crisis in 1979-80, which aggravated and extended a round of spirit-breaking domestic inflation and international political instability;

A rescue by American coal of European allies caught short of oil in the harsh winters that followed;

A consequent replacement in the U.S. economy of oil by lower-cost coal, which was attended by a 25 percent increase (though 1986) in surface mine production while mastering the demands of a new law;

A lessening in demand for oil;

An ultimate fall in the price of oil, to which replacement by coal was a major contributing factor, as well as

The successful reclamation of 1.4 million acres of land -- roughly the equivalent of the state of Delaware -- mined to replace that oil; and

The return of that land to its original characteristics and to other more productive uses, which makes mining only a temporary land use; and

The restoration of 6,000 sites in Appalachia, which leaves another 6,000 to go under the abandoned mine lands program.

Much has been accomplished, and more will be accomplished.

One of the flaws Udall criticized -- the exemption from regulation of mines of two-acres or less -- has been repealed with the full support and urging of the coal industry.

The other major abuse is wildcat mining -- that is, mining by roving, unpermitted and quick-striking freebooters who can be in and out of small, isolated Appalachian sites in less than a month. Though few in number, they ignore all laws. The industry supports and is cooperating in finding aggressive ways to put wildcatters out of business.

Laws, like automobiles and airplanes, are devices for moving forward. Perfection comes with use, experience and modification. Both the automobile and the airplane are still being perfected. The same is true of laws, particularly this one.

Richard L. Lawson

The writer is president of the National Coal Association.