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A fast neutron irradiation system was designed for performing activation analyses with fast neutrons on elements producing short-lived nuclides. The system consists of a Van de Graaff accelerator, a pneumatic transfer system, a γ-ray detection system and a control system. All the process steps of the activation analysis, such as irradiation, transfer of the sample and measurement of γ-rays are carried out in automatic sequence, governed by a programmed control system. The main part of this paper is devoted to a description of this control system. The apparatus was successfully tried for the analysis of 207mPb (T1/2=0.797 sec). The activity was identified with the apparatus set to measure half-life. Background can be reduced by select-ing the time sequence of analyzing processes.

WHEN A RELATIVELY LARGE number of values, such as constants or random values of a variable, are to be used by the calculator, and further, when these values are to be used in a prescribed order, they may be supplied to the machine via one of the interpolator mechanisms and a perforated paper tape. Such a tape is known as a “value tape” to distinguish it from a functional tape. Mathematically, the operation of reading from a value tape is the equivalent of zero order interpolation. In order to increase the flexibility of the interpolators when used in this manner, three sequence codes have been assigned to each interpolator mechanism. These require that the tape be stepped forward, stepped back, and that the sensing pins read from the tape.

Mechanisms designed to carry out the ordinary operations of decimal arithmetic were invented several centuries ago, and indeed Charles Babbage, in England, conceived automatic sequence control over one hundred years ago. The modern electronic high-speed computer based on binary Boolean logic has other ancestors besides decimal mechanical calculators in its pedigree, however. The mechanical realization of binary logic is generally credited to William Stanley Jevons, British economist and logician, in 1869. 2 This mechanism is an ancestor of the modern computer on the binary side of the family. It has recently come to light that an American university professor designed what is probably the first electric binary logic machine, and this is very likely the first design of an electric data processor of any kind.

Structural properties, local and asymptotic, of members of a class of simple, realtime generable sequences are analyzed.

Ever since the development of automatic sequence computers it has been possible for the machine to modify its own instructions, and this ability is the greatest single faculty in the complex that tempts the term "giant brain." Friedberg demonstrated a new technique in the modification of instructions; he allowed the machine to make alterations at "random," and lent direction to the maneuver by monitoring the result. This technique is far from being a feasible way to program a computer, for it took several hundred thousand errors before the first successful trial, and this was for one of the simplest tasks he could imagine. A simple principle of probabilities shows that a task compounded of two tasks of this same complexity would take several hundred thousand times as long, perhaps a million computer hours. It is the object of this study to examine techniques for abbreviating this process.

THE black mark earned by the government of the day more than a hundred years ago for its failure to see Charles Babbage's difference engine brought to a sucessful conclusion has still to be wiped out. It is not too much to say that it cost Britain the leading place in the art of mechanical computing. Babbage then conceived and worked on his ‘analytical engine’, designed to store numbers and operate on them according to a sequence of processes conveyed to the machine by cards similar to those used in the Jacquard loom. This, however, was never completed. A Manual of Operation for the Automatic Sequence Controlled Calculator By the Staff of the Computation Laboratory. (Annals of the Computation Laboratory of Harvard University, Vol. 1.) Pp. xiii + 561 + 17 plates. (Cambridge, Mass.: Harvard University Press; London: Oxford University Press, 1946.) 10 dollars.

THE new I.B.M. Automatic Sequence Controlled Calculator at Harvard was recently described in Nature (158, 567; 1946). The volume now before us contains the first of a series of tables produced by the machine in its spare time ! Tables of the Modified Hankel Functions of Order One-Third and of their Derivatives By the Staff of the Computation Laboratory. (Annals of the Computation Laboratory of Harvard University, Vol. 2.) Pp. xxxvi + 235. (Cambridge, Mass.: Harvard University Press; London: Oxford University Press, 1945.) 10 dollars. 558.