Probably the best example of this type of mounting applied to a refractor is that made by the elder Cooke of York for Fletcher of Tarnbank; the polar axis is of cast iron and the mounting very satisfactory and convenient, but unfortunately no detailed description has been published.

Fraunhofer's chef-d'oeuvre, the great Dorpat refractor, made for Otto Struve about 1820, had a mounting of this type, and was the first equatorial of any importance to be provided with clockwork.

The largest example of his work is the refractor of 24-in.

refractor to enable it to take part in the International Photographic Survey of the Heavens.

refractor by a handle which, when used, affects very injuriously the rate of the clock for the time being.