When asked about the new Rhodesian biracial government, Salisbury's deputy mayor, Jack Whiting, likes to refer to remarks by Abraham Lincoln during a critical time in the Civil War.

Lincoln asked his listeners what they would do if they saw Blondin, a famous 19th century tightrope artist, walking across Niagara Falls. "Would you shake the rope while he was passing over it? Or would you tell him to stoop more, or go a little faster? No. You would hold your breath as well as your tongue until he was safely over."

Like Blondin's audiences, many Rhodesians, black and white, are holding their breath and tongues and reserving judgment on Rhodesia's experiment in black-white rule as it passes through its most critical phase since it was created by the March 3 agreement between Prime Minister Ian Smith and three moderate black leaders.

"It's all very confusing," said Bradden Ngwerume, 26, a blck who is a car-rental agent. "We haven't seen any changes yet, so we have to wait and see what happens," he said, voicing a common sentiment.

All the same, the public is beginning to add up what the government has done so far - and what it has failed to do - in order to judge whether it is actually moving toward its stated goal of black majority rule with strong constitutional gurantees for the white minority.

Supporters of the interim government point out that it has released more than 700 political detainees, has lifted the bans on two political parties linked to guerrilla forces - the Zimbabwe African People's Union (ZAPU) and the Zimbabwe African National Union and ha offered an amnesty to all guerrillas agreeing to law down their arms.

They also note how black and white coministers in several Cabinet offices are cooperating better than was thought possible.

Critics of the government say that the release of detainees if long overdue and, according to Josiah Chinamano, a ZAPU vice-president, many of the remaining 200 detainees are ZAPU supporters and officials who oppose the current government. Their cases are being reviewed by the government.

While restrictions on political activity have been loosened greatly, there is not yet complete freedom of speech. Students from the local university who demonstrated against the interim government were arrested and given three-month suspended sentences at hard labor. In contrast, supporters of the interim government who pelted Secretary of State Cyrus Vance's car with eggs when he was here three weeks ago were not arrested.

The Zimbabwe Times, the country's only black-oriented newspaper, which in financed by the mining empire of Tiny Rowlands, was ordered not to print remarks made by Byron Hove, the black justice minister fired a week ago for his outspoken views. The pro-government Rhodesia Herald, however, was not given such an order.

Finally, critics have questioned the government's lack of action in some fields. "Hardly anything has been attempted to remove racial discrimination, the root cause of our troubles," said a statement by the United African National Council led by Bishop Able Muzorewa, one of the three black leaders who formed the government with Smith.

For example, clauses in deeds restricting the sale of homes in certain neighborhoods to whites are still in force.

And although plans to start the process toward elections and full black majority rule have been discussed, nothing concrete has yet been done.

Blacks are looking for visible changes in the bureaucracy, which is predominantly white. Before he was fired, Hove applied for a new secretary, a black reporter related. "The white ladies were all very eager, Hove told me, but the trouble was, none of them spoke Shona," Hove's African language, the reporter said. "They are moving too slowly," he added.

The government is not moving faster for a definite reason - in order not to upset the white population, especially before the whites only referendum Smith has promised to hold in order to get approval of his decision to accept majority rule.

A factor that will be decisive in garnering the support of blacks and whites for the experiment in biracial rule is the success of some weekend jaunts into the countryside by Muzorewa and another of the black leaders. The Rev Ndabaningi Sithole.

They are meeting guerilla leaders to try to convince them to accept the offer of amnesty announced by the government last week. If significant numbers of guerrillas do join the government, and the war winds down, the government will undoubtedly gather much support.

Success in the amnesty program would do much to offset several serious adverse consequences of the firing of Jove.

First, black swere angered by the dismissal because they agreed with Hove's calls for fundamental changes in the police and judiciary to reflect majority rule. He was fired by the ruling four-man Executive Council when he refused to retract the statements.

Second, a subsequent threat by Muzorewa to pull out of the government and his denials that he was involved in the decision to fire Hove - even though two of his Executive Council colleagues, Sithole and Chief Jeremiah Chirau, said he was - brought a crisis of confidence in the new government.

"I don't know much about politics," said Ruth Maena, "But it seems that four in the Executive Council are not talking the same language. It makes anyone with a brain wonder."

The Hove affair, observed another black professor, "has left a bad taste in the mouth."

There are, however, people who have already made up their minds about the internal settlement.They opposed it because it excludes the guerrilla leaders living outside the country, Jushua Nkomo and Robert Mugabe.

Ariston Chambati, is an acting secretary general of Nkomo's ZAPU, whose guerrillas are waging a bush war against Rhodesian forces. Since the government lifted the ban on ZAPU last week, Chambati is no longer prohibited from addressing public meetings. On Friday, he roundly condemned the internal settlement at a lunchtime gathering of black and white city employees just one block down the street from Smith's office.

"The purpose of the March 3 agreement is to groom a black government to take over from the Rhodesian Front [Smith's party] in the image of the Rhodesian Front," Chambati said. He attacked the provisions of the agreement which he said left the army, police, civil service and judiciary heavily under white control.

Most of the questions Chambati got after his speech were from the whites. They wanted to know what he meant when he said that ZAPU wanted the civil service and bureaucracy to be "restructured." To the anxious white questioners, it appears to mean losing their jobs to a black unless there are safeguards in the constitution for them.

Although the internal settlement is meant to be a compromise between the fears of the whites and the aspirations of the blacks, both groups are worried. The whites fear that the future black-run government will disregard them. The blacks fear that the black-run government will be so heavily circumscribed by constitutionally entrenched guarantees for whites that it really will not be majority rule.

"People are worried, because they see what they had hoped for was just a dream. What the people want is true majority rule under black rule," said Edward Pswarayi, in his medical clinic in the all-black community of Highfield.

"We are not against whites, but they have had too much, for too long at the disadvantage of so many people."