1From Thomas Jefferson to Francis Hopkinson, 3 January 178[6] (Jefferson Papers)
...as the metal hitherto used, for the specula of telescopes. These two properties had...
2From Thomas Jefferson to David Rittenhouse, 25 January 1786 (Jefferson Papers)
...polish as the metal heretofore used for the specula of telescopes, is inattackable by rust as...
3From Thomas Jefferson to Benjamin Franklin, 27 January 1786 (Jefferson Papers)
...thought of using the metal Platina for the specula of telescopes. Indeed I believe the thought...
4From Thomas Jefferson to James Currie, 28 January 1786 (Jefferson Papers)
...called Platina to the purpose of making the specula of telescopes. It is susceptible of as...
5From Thomas Jefferson to Ezra Stiles, 1 September 1786 (Jefferson Papers)
...of the mixed metal of which the specula were formerly composed. It is insusceptible of...
6Thomas Jefferson to John Vaughan, 24 April 1813 (Jefferson Papers)
...describing them as “Observationes Siderum habita Pisis in Specula Academica ab ano 1778 ad...
7Thomas Jefferson to Robert Patterson, 13 October 1815 (Jefferson Papers)
or the mixt metal of the telescopic specula, or even of common glass mirror, with cross