Mark IV, the latest and most advanced of Harvard's calculators, will probably be completed about mid-May, Howard H. Aiken, director of the Computation Laboratory, reported this week. Aiken also explained that the lab's activities now include the fields of economics, bible reading, optics, and the analysis of jet engines.

Mark IV is expected to be about 250 times faster than its prototype, Mark I, and will cost from $300,000 to $400,000. Mark II and Mark III, the other mechanical brains, were also built at the Computation Lab next to the Graduate Center, but they are now at the Naval Proving Ground in Virginin.

Typical of the problems that were too complex for solution before the Marks arrived is Economics Professor Wassily W. Leontief's General Equilibrium Theory. Covering the alternatives possible from production, the theory in especially useful in the allocation of short materials. The advanced stages of this work are so complicated that Leontief must wait for the completion of Mark IV to proceed with his research.

His new analysis method, which graphically plots both an entire economy and its intricate interrelations, enables government and industry planners to gauge beforehand the effects of a shortage, a surplus, partial unemployment of the nation's economy, or a wage hike.

In the past, economists, unable to handle the huge masses of empirical data necessary for such projects, tended to oversimplify and to build "display cabinets without displays," comments Leontief. But the invention and development of the computer has lessened the reluctance to work problems which require heavy computation.

Simplest Theory

The simplest theory covering an economy of two involves 14 equations, and as the population goes up, the number of equations required increases in geometric fashion. With modern computers, socialist planners may be able to fill the function which producer and consumer handle in a free economy through millions of individual deals.

Leontief hesitates to use the word "predict" when he talks about the possible consequences of his work, but readily asserts that his figures should be able to "narrow down the range of economic possibilities until probabilities are pin-pointed."

He cautions that variables such as new inventions and changes in government policies are unpredictable and can effect the practical validity of Mark's computation.

One of the first projects to be handled by Mark IV will be to "read" copies of the Bible under the direction of the Reverend John W. Ellison of Tucson, Arizona. Ellison will spend two weeks supervising the "reading" of 100 ancient manuscripts of the Bible, two at a time. The machine will indicate where words have been added or deleted, as well as differences in spelling and word order.

Helping the Government

Government work of Mark I included an assignment for the Air Force when it was planning to construct a model of a jet engine with a takeoff unit incorporated in it. Mark I proved this development impractical and the Air Force cancelled their order for the model. According to Aiken, the money that Mark I saved the taxpayers would be sufficient to run the computer for two and one-half years.

In the field of optics the computer is giving added evidence of its versatility. Mark I is able to trace mathematically rays through aerial lenses while plans for the lenses are still on the drawing board. This frees the opticians from their tedious calculating duties and enables them to work exclusively on developing advanced optical designs.

While taking breathers between problems. Mark I has ground out 26 volumes of mathematical tables to be printed by the University Press.

The Operating Technique