Sciographia, or The Art of Shadows

The Churches of the United Kingdom have always had a major need to measure time. Time of day was very important in religious houses and before watches the church was the sole arbiter of time of day. The calendar was needed to tell the laity the occurrence of Saints’ Days and major festivals, such as Easter. Many devices were kept in great houses and religious establishments for this purpose: the Staffordshire clog is just one such device.  It is not surprising, therefore, that there are numerous references in the Worcester Cathedral library to books with sections on the construction of sundials: vertical, horizontal and sloping. These span a period from the 1500s to the 1700s with texts in Latin and English.

Sundials indicate the time by casting a shadow or throwing light across a ‘dial face’ or a ‘dial plate’, often marked with hour lines.The movements of the sun and the shadows it casts have been used by humans to tell the time for millennia. Ancient Egyptian obelisks from as early as 3500 BC, which symbolised the Sun God Ra, are thought to have been used in this way.

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From ‘Antiquity Explained’ by Montfaucon (1721). Image copyright the Dean and Chapter of Worcester Cathedral (UK).

Although sundials had been constructed and used since ancient times, the proliferation of texts about them in the Early Modern period may suggest that the general public’s need for a way of measuring time was growing greater. One book held in the library, entitled ‘Sciographia, or The Art of Shadowes’ by John Wells (1635), is addressed ‘To the Lover of the Mathematiques’.

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Title page of ‘The Art of Shadowes’ by John Wells (1635). Image copyright the Dean and Chapter of Worcester Cathedral (UK).

In the foreword, Henry Gellibrand describes the importance of understanding the art of shadows:

Neither stands this Art of Shadowes in any darke or inferiour Place; for by them are we led on to many rare and sublime speculations. It is from Shadowes wee argue the cause of Eclipses, their Quantitie and Qualitie; The Magnitudes of the Luminaries and their Altitudes; From them we obtaine the Longitudes and Latitudes of places; distinguish the Zones, Climes, and Paralels; They first taught us the Sphericall Figure of the Earth, its Magnitude, and Disproportion to the vast Universe; … In a word, it is this Art of Shadowes which rectifieth our Account of Time

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Chapter 1 of ‘The Art of Shadowes’ (1635). Image copyright the Dean and Chapter of Worcester Cathedral (UK).

The book contains sections on trigonometry, geometry and logarithms as well as specific instructions on how to construct and use sundials. It is an impressive work of seventeenth-century mathematics.

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Diagram of a sundial from ‘The Art of Shadowes’ (1635). Image copyright the Dean and Chapter of Worcester Cathedral (UK).

Keith Roe

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