1Thomas 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
2Thomas Jefferson to John Vaughan, 24 April 1813 (Jefferson Papers)
...describing them as “Observationes Siderum habita Pisis in Specula Academica ab ano 1778 ad...
3John Vaughan to Thomas Jefferson, 19 April 1813 (Jefferson Papers)
Observationes siderum habitae Pisis in specula academica (Slop von Cadenberg) [index entry] specula
4From 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...
5Remarks on Observations with a Sextant, 18 April 1803 (Jefferson Papers)
...true, will be fainter than that from the specula, unless the Telescope of the Sextant be...
6From 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...
7From Benjamin Franklin to Peter Collinson, 5 November 1756 (Franklin Papers)
...S., 1737; recognized as the foremost maker of glass specula of his day.
8To Thomas Jefferson from John Ledyard, 19 March 1787 (Jefferson Papers)
...I saw the reason—the true reason in the specula of the secretarys eye—and so damn his eyes—...
9Thomas Skidmore to Thomas Jefferson, 18 August 1822 (Jefferson Papers)
...is “an alloy of copper and tin used for making specula” (
10From 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...