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The majority of Arab weather prognostics are, as might be expected, concerned with the winter season, when the changeable weather gives scope for forecasting. The summer months in most Arabic-speaking lands are rainless, and except for wind changes offer little or no field for the activity of the weather prognosticator. The sun and moon, the stars, the rainbow, mist, dew, thunder and lightning, birds and insects all form constituents in Arabic weather forecasts.

Introduction An investigation into the causes of blindness in the Netherlands made by one of us (J.S.K.) has confirmed the assumption that connatal cataract is one of the main blinding causes in the Netherlands. Of 4,300 known blind persons, 197 were blind following bilateral operation for connatal cataract, i.e., 4.6%. Of these, 75 were children (up to the age of 18) and 122 were adults. These 75 children form approximately 10% of all the blind children in the Netherlands. A visual acuity of 5/60 or less is taken to indicate blindness in children. The upper limit for partial sightedness in children is taken as 3/10. The aim of the present study was to establish, if possible, the cause(s) of blindness or partial sightedness in those cases of connatal cataract in which the operations were apparently technically well performed, and to outline a method indicating the prognosis of the ultimate visual

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A US Navy strategy was generated and is still evolving to develop and demonstrate diagnostics and prognostics for helicopter drive trains. The SH-60 program was initiated as a proof-of-concept effort to develop, demonstrate, and integrate available and advanced mechanical diagnostic technologies for propulsion and power drive system monitoring. Included in these technologies were various rule based and model based analysis techniques which were applied to demonstrate and validate various levels of diagnostic and prognostic capabilities. Since spalling of the SB 2205 roller bearing integral inner race is the most common dynamic component cause for gearbox removal in the SH-60, it was tested as part of the original HIDS effort. Using this as a case example, diagnostic methods are used to identify the fault, and means of applying prognostics are discussed. Other more recent examples of "seeded faults" are also discussed as case studies demonstrating various degrees of diagnostic and prognostic capabilities. These include the evaluation of an epicyclic planet gear separation algorithm developed by the DSTO, Australia. Multivariate analysis reasoners, and information fusion requirements and approaches are also discussed. Most recently a strategy is evolving to more fully develop and demonstrate the predictive aspects of prognostics. Finally a full description, recent accomplishments, status and plans for the NAWCAD Helicopter Transmission Test Facility is presented.

THE form of cloud represented by Prof. Poey in his figure a, in this week's NATURE, is very similar to that described by the Rev. C. Clouston, LL.D., in his “Explanation of the Popular Weather Prognostics of Scotland,” published by A. and C. Black in 1867, and also in Dr. Mitchell's paper “On the Popular Weather Prognostics of Scotland,” Edin. New Phil. Journal, Oct. 1863.

The following considerations are a first attempt at formulating [internal] laws for the historical evolution of physics — a task as yet unsolved by historiography [of science]. The practical value of this attempt resides in the fact that [the knowledge of] such evolutionary laws provides a scientific basis for prognostics and research strategy that cannot be obtained in any other way.

The H 0n modes for helical waveguide are obtained rigorously from a newly introduced system of coordinates. It is also found that a coaxial line can support slow waves of magnetic type.