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Published online by Cambridge University Press: 10 November 2010
Astronomy, instead of merely being an amusement, became my chief study. It occupied many of my leisure hours. Desirous of having the advantage of a Reflecting Telescope of large aperture, I constructed one of twenty inches diameter. In order to avoid the personal risk and inconvenience of having to mount to the eye-piece by a ladder, I furnished the telescope tube with trunnions, like a cannon, with one of the trunnions hollow so as to admit of the eye-piece. Opposite to it a plain diagonal mirror was placed, to transmit the image to the eye. The whole was mounted on a turn-table, having a seat opposite to the eye-piece, as will be seen in the engraving on the other side.
The observer, when seated, could direct the telescope to any part of the heavens without moving from his seat. Although this arrangement occasioned some loss of light, that objection was more than compensated by the great convenience which it afforded for the prosecution of the special class of observations in which I was engaged; namely, that of the Sun, Moon, and Planets.
I wrote to my old friend Sir David Brewster, then living at St. Andrews, in 1849, about this improvement, and he duly congratulated me upon my devotion to astronomical science.
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