Sometimes, small happenings shed a clearer light on basic questions than do events of much greater magnitude. In the last couple of weeks, some small happenings have helped illuminate the character of the Reagan administration.

One such event was the disclosure that Attorney General William French Smith had signed himself up for a pair of tax-shelter investments that gave him first-year deductions of more than $117,000 on an out- of-pocket expenditure of less than $30,000.

The investments were made personally by Smith, who has put most of his assets in blind trust, and were disclosed--in one case, belatedly--in his required disclosure statement. The deals involving the nation's chief law-enforcement officer are assertedly legal, but they are of the type of high-multiple, precariously leveraged, late-in-the-year, smart-operator transactions that almost automatically draw the Internal Revenue Service's skeptical audit. According to his spokesman, Smith saw nothing wrong with looking for the financial edge he might gain if his shelter got past the IRS scrutiny.

Nor did he blink when his pal and fellow-member of Ronald Reagan's kitchen cabinet, Earle M. Jorgenson, had the board of directors of his company vote Smith a $50,000 "severance payment," when Smith stepped down from the company's board of directors eight days before Reagan's inaugural.

That one is under official scrutiny from the Office of Government Ethics, because private sources are not allowed to supplement officials' salaries. Smith, who drew $500 per meeting during the six years he served on Jorgenson's board, is apparently the only retiring director ever to walk away with such a handsome sum, and the government wants to know why he was singled out for reward.

A few days after Bob Woodward of The Post laid out the Smith financial saga, Jorgenson's name turned up again as one of those who showered more than $30,000 worth of personal gifts on President and Mrs. Reagan during their first year in the White House. In Jorgenson's case, it was a $150 sweater for his old friend, the president. That was a mere bagatelle, inasmuch as Jorgenson had also contributed $50,000 to Nancy Reagan's White House redecoration project.

There is a pattern to this, a pattern that appeared much earlier in Reagan's career. Jorgenson, Smith and the other kitchen cabineteers are all members of the wealthy circle that staked Reagan to his start in California politics 17 years ago. When he was elected as governor, they bought and furnished an "official residence" for the Reagans to use in their Sacramento years. And now they continue to make life comfortable for their friends.

There is no doubt of their friendship. When the Reagans go home to California, as they are doing again this week, these are the people they see. And every time Reagan is with them, he comes back fortified in his belief that cutting taxes and government spending is the noblest work of man.

The pattern in this is an artful blending of private gain and public service that conveniently obliterates the distinctions that statute and custom have tried, over many years, to build into a concept of official ethics.

It is not peculiar to this administration or the Republican Party, but it represents a distortion of values and an abuse of privilege to which conservatives of a certain kind are particularly prone.

Theirs is a conservatism, not of conscience, but of convenience. It accepts the morality of the marketplace as the measure of public rectitude. Cloak it in whatever pieties they may, these conservatives really believe that it is the bottom line that counts.

But, oh, how they love the pieties. The president set the stage for the past week's disclosures by endorsing a school-prayer amendment, another little action that shows how far his conservatism of convenience departs from principled conservatism. Such conservative justices as Tom Clark and Robert H. Jackson wrote the opinions a generation ago, laying out in conservative rhetoric why the government may not constitutionally endorse, sponsor or recommend any form of official prayer. But their lesson is lost on Ronald Reagan.

As is his custom, the president said he would have his pal, William French Smith, provide the language of the proposed constitutional amendment that would restore prayer to school classrooms. The draft submitted Monday was pretty bland.

The prayer that seems appropriate, under the circumstances, would go like this: "Dear Lord, take good care of Your people, just as we take care of each other."