Pl. spectra (also spectrums). [L. spectrum: see SPECTRE sb.]
1. An apparition or phantom; a spectre.
1611. Speed, Hist. Gt. Brit., IX. xiv. (1632), 770. Walsingham hath written of a fatall Spectrum or Apparition,… where sundry monsters of diuers colours … were seen.
1649. Bulwer, Pathomyot., II. ii. 140. Feare also, and a Sudden fright or Spectrum … hath the same effect sometimes upon the Muscles of the Face.
1684. Case of Cross in Baptism, 14. Startled at Thunder, taken in a storm, frighted with a spectrum.
1706. Baynard, Cold Baths, II. 309. He would sooner believe Witch-Craft and Spectrums.
1728. Brice’s Weekly Jrnl., 19 July, 1. The Maid’s seeing his Spectrum, could be no … Deceptio Visus, but … was a real Apparition of the Deceased.
1809. W. Irving, Hist. New York (1861), 182. Subject to bad dreams … in the night, when the grizzly spectrum of old Keldermeester would stand sentinel by his bedside.
1860. Ruskin, Mod. Paint., V. IX. xi. 326, note. Fuseli may wander wildly among gray spectra, but Reynolds and Gainsborough must stay in broad daylight, with pure humanity.
fig. 1657. H. Pinnell, Philos. Ref., 67. The Spectrum, ghost, or fantasie, the Light of Nature.
1674. Grew, Anat. Pl., Disc. Mixture (1682), 222. Their notions of Mixture … being … so many phantastick Spectrums, serving only to affright men from coming near them.
1710. Sacheverell, Answ. Bp. Oxford’s Sp., 21. I was … surpriz’d … with an Apparition or Spectrum, which the Magi call a Parenthesis.
1866. Huxley, Physiol., x. 247. Many persons are liable to what may be called auditory spectra—music of various degrees of complexity sounding in their ears, without any external cause, while they are wide awake.
2. An image or semblance. rare.
1693. Penn, Fruits Solitude, II. § 197. A jealous man only sees his own spectrum, when he looks upon other men, and gives his character in theirs.
1831. Carlyle, Sart. Res., II. viii. Two little visual Spectra of men, hovering … in the midst of the Unfathomable.
3. The colored band into which a beam of light is decomposed by means of a prism or diffraction grating.
1671. Newton, in Phil. Trans., VI. 3076. Comparing the length of this coloured Spectrum with its breadth, I found it about five times greater. Ibid. (1674), IX. 218. The Sun-beams … passing through a glass Prism to the opposite wall, exhibited there a Spectrum of divers colours.
1728. Pemberton, Newton’s Philos., 323. These colours … shall discover themselves more perfectly … the larger the spectrum is.
1788. V. Knox, Winter Even., I. iii. 27. All the hues of the prismatic spectrum.
1815. J. Smith, Panorama Sci. & Art, I. 440. It assumes an oblong shape,… and exhibits seven different colours. This oblong image is called the spectrum, and from its being produced by the prism, the prismatic spectrum.
1839. G. Bird, Nat. Philos., 326. The solar spectrum may therefore be regarded as composed of three spectra of equal lengths overlapping each other.
1879. Cassell’s Techn. Educ., I. 126/1. Most of our sources of artificial light yield spectra without lines.
fig. 1860. Holland, Miss Gilbert, iv. 68. All the colors of the spectrum of truth.
1874. H. R. Reynolds, John Bapt., viii. 453. A luminous spectrum lingers for a while in the atmosphere of Judaism.
4. The image retained for a time on the retina of the eye when turned away after gazing fixedly for some time at a bright-colored object.
1786. Phil. Trans., LXXVI. 313. This appearance in the eye we shall call the ocular spectrum of that object.
1829. Nat. Philos., Optics, xvii. 46 (L.U.K.). One of the most curious affections of the eye, is that in virtue of which it sees what are called ocular spectra, or accidental colours.
1839. G. Bird, Nat. Philos., 398. Thus wafers, or other coloured objects, produce spectra of colours complementary to their own.
1854. Lardner’s Mus. Sci. & Art, I. 85. Unreal objects will often be perceived. These are called spectra. Ibid. This object is an optical spectrum.
5. Ent. A spectre-insect (Phasma).
1838. Murray’s N. Germany, 34. The minerals and insects are also good; among the latter are various specimens of spectrum, nearly a foot long.
6. attrib. (in sense 3): a. Spectrum analysis (cf. SPECTRAL a. 5 b). Also fig.
1866. Atkinson, trans. Ganot’s Physics, 425. The method of spectrum-analysis is most readily applied to the alkaline metals.
1871. trans. Schellen’s Spectrum Anal., Pref. 4. The great merit of the book as a popular treatise on Spectrum Analysis.
1873. Farrar, Famil. Speech, ii. 39. The microscope and spectrum analysis of Philology.
b. Misc., as spectrum-band, -line, microscope, photography, work.
1871. trans. Schellen’s Spectrum Anal., 10. The number of the spectrum-lines of a substance. Ibid., 456. Qualitative Analysis … by means of the spectrum microscope.
1889. V. Schumann, in Anthony’s Photogr. Bull., II. 389. The bath plate is less suitable for spectrum photography. Ibid. (1891), IV. 357. So intensely does it appear from the yet hardly visible spectrum band.
1899. Lockyer, in Daily News, 13 Nov., 6/7. For this spectrum work very rapid isochromatic plates … should be employed.
