Sir, - Brendan McWilliams, in his contribution on sunspots (September 6th), referred to the phenomena of the solar 11 year cycle, discovery of which has been attributed to the German scientist, H S Schwabe, in 1848. However, the records of Chinese celestial observations, which are still available and which span 4,000 years, contain extensive data on sunspots.
These were analysed as recently as 1975 by the Yvannan University for the period 43 BC to 1638 AD, during which time 106 observations were recorded. The result showed a solar cycle of 10.6 years, with an error ratio of +/- 0.43 years. This in spite of the fact that observations were, when possible, by the naked eye, or by the sun's reflection in static oil.
The accuracy and value of the Chinese records were recognised by the famous scientist and scholar, Dr Joseph Needham. In his book Science and Civilisation in China, he observed, that the Chinese "were often far in advance of contemporary Europe", a point of view supported by the American astronomer, George Ellery Hale who said that the Chinese were "roughly 20 centuries ahead of Westerners in sunspot observation".
While amused by Mr McWilliams's wry comment on those who attempted to equate plague in China with the advent of sunspots, one can agree with his view that by their influence on the level of ultraviolet radiation, they can influence our Irish weather patterns. - Yours, etc.
Social and Industrial Research,
Ballsbridge Terrace,
Ballsbridge, Dublin 4.