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Your article on Polykleitan proportions (THES, May 31) makes me wonder if they were the causes of the application of modular design in Greek catapults about 300 years later.

The dimensions to be given to the various parts of these weapons were laid down in manuals in terms of a module (D) derived from the length or mass of the missile to be projected, on a basis which nowadays would be described as "dimensionally correct". For example: D(dactyls) - 1.1 (mass in drachmae)1/3 Calculations show that the proportions of the various parts encapsulated in this modular system were well-balanced, suggesting an evolutional process, although there were serious shortcomings in other aspects of the design. It might be that the Greeks perceived that a modular form corresponded to fitness for function in all sizes (though this is not always true, for example, not in plants).

Michael French

Engineering department

Lancaster University