▪ I. † ˈspectral, n. Obs. rare.
[Cf. next.]
An apparition; a spectre.
| a 1656 Ussher Ann. (1658) Ep. to Rdr., Those things which I produce concerning Preesages, Spectrales, and Oracles. Ibid. 705 He expounded to him out of the doctrine of the Epicureans, what was to be thought concerning such spectrals. |
▪ II. spectral, a. (
ˈspɛktrəl)
[ad. L. type *spectrāl-is, f. spectrum spectre and spectrum. So mod.F. spectral.] † 1. Capable of seeing spectres.
Obs.| 1718 F. Hutchinson Witchcraft v. 81 Joseph Ballard..sent to Salem, for some of these Accusers, who pretended to have the spectral Sight, to tell him who afflicted his Wife. |
2. a. Having the character of a spectre or phantom; ghostly, unsubstantial, unreal.
| 1815 Shelley Alastor 259 The mountaineer, Encountering on some dizzy precipice That spectral form. 1818 Scott Br. Lamm. xiii, Some of the spectral appearances which he had heard told of in a winter's evening. 1853 Kane Grinnell Exp. xxxiv. (1856) 307 The setting sun..gave us again the spectral land about Cape Adair, eighty miles off. 1877 Black Green Past. xlii, We saw through a window a wild vision of a pair of spectral horses apparently in mid-air. |
| fig. 1829 I. Taylor Enthus. viii. 191 A spectral resemblance of piety, unsubstantial and cold as the mists of night. 1837 Dickens Pickw. xxiv, A spectral attempt at drollery. |
| Comb. 1840 A. M. Hall Irish Peasantry (1850) 138 A lean, spectral-looking gray horse..limped towards them. 1868 Boyd Less. Middle Age 315 A mile or two down,..tall and spectral-white, stands the Cloch lighthouse. |
b. Resembling, looking like, suggestive of, a spectre or spectres. Also
spec. in
Zool.| 1828 Lytton Pelham xviii, The spectral secretary of the embassy. 1843 A. Bethune Sc. Fireside Stor. 110 That species of erect tombstone, which some one has somewhere designated ‘spectral’. 1851 Ruskin Stones Ven. (1874) I. App. 366 The old spectral Lombard friezes. 1884 Coues N. Amer. Birds 509 Strix cinerea,..Spectral Owl. 1896 H. O. Forbes Hand-bk. Primates I. 20 The Spectral Tarsier. |
3. Characteristic of, appropriate to, a spectre.
| 1820 Byron Mar. Fal. v. ii, They form'd a spectral voice, Which shook me in a supernatural dream. 1852 A. Jameson Leg. Madonna Introd. (1857) 25 Compared with the spectral rigidity, the hard monotony, of the conventional Byzantines. 1898 Watts-Dunton Aylwin i. vi, Crumbling cliffs, whose jagged points..had the kind of spectral look peculiar to that coast. |
4. Produced merely by the action of light on the eye or on a sensitive medium.
| 1839 G. Bird Nat. Phil. 398 If the wafer were yellow, and placed on a black surface, the spectral image will be deep violet when viewed on a white ground; in the same manner a white wafer is attended by its black spectral figure. |
5. a. Of or pertaining to, appearing or observed in, the spectrum. Also applied to a property or parameter which is being considered as a function of frequency or wave-length, or which pertains to a given frequency range or value within the spectrum.
Cf. spectrum 3 a, b.
| 1832 Nat. Philos. (L.U.K.) II. Index 40 Spectral colours, when re-united, produce white. 1849 M. Somerville Connex. Phys. Sci. (ed. 8) xxiv. 235 A spectral image obtained by Mr. Hunt on a similar [Daguerreotype] plate. 1866 Atkinson tr. Ganot's Physics (ed. 2) §480. 424 The relative distances of the different spectral lines. 1879 O. N. Rood Mod. Chromatics x. 127 By mixing three or more spectral colours no new hues were produced. 1883 19th Cent. Nov. 881 Its absorptive capacity for particular spectral tints. 1919 Sci. Abstr. A. XXII. 563 Section 2 considers the definition of temperature. This is based upon thermal radiation and spectral distribution. 1950 Audio Engin. Aug. 14/2 A knowledge of the spectral characteristics of sound sources will indicate the regions in the frequency scale to which particular attention must be paid in assessing the effect of response changes in the sound system. 1951 New Biol. XI. 34 A spectral absorption curve, in which the proportion of light absorbed is plotted against wavelength. 1957 G. E. Hutchinson Treat. Limnol. I. vi. 376 The spectral composition of the total reflected light when the sun is high is little different from that of the incident. 1964 Oceanogr. & Marine Biol. II. 13 The turbulent fluctuations of velocity or of some other property of the water..may be observed directly, and the spectral distribution of energy..derived from the observations. 1966 McGraw-Hill Encycl. Sci. & Technol. IV. 582/2 Any spectral emissivity value is valid only for a narrow wavelength interval. 1971 Physics Bull. July 385/2 Spectral intensity is intensity per unit bandwidth (W sr-1 Hz-1). Ibid. Nov. 653/3 An investigation of the spectral content, vibrato, attack and sound pressure of vowels sung by male and female students under technical and performing conditions. 1977 I. M. Campbell Energy & Atmosphere viii. 272 The spectral absorption characteristics of alkyl nitrates are rather similar to those of nitric acid. |
b. Carried out or performed by means of the spectrum.
| 1879 Proctor Pleas. Ways Sci. i. 26 The inquiry seems specially suited to the methods of spectral photography pursued by Dr. Draper. 1881 Times 11 Mar., Spectral observations on stars. |
c. Math. Of or pertaining to the spectrum of a transformation (
spectrum 6).
| 1948 P. R. Halmos Finite Dimensional Vector Spaces ii. 80 The characteristic equation, and consequently every other spectral concept such as the proper values and their multiplicities, is invariant under replacing A by BAB-1. 1968 P. A. P. Moran Introd. Probability Theory iii. 118 Hence U and V are non-singular matrices, and we have P = U-1λU = VλV-1, which is a ‘spectral’ decomposition of P. |
6. Special collocations:
spectral analysis, chemical analysis of substances by means of their spectra; analysis of light or another oscillating system into a spectrum;
spectral index (see
quot. 1956);
spectral series = series n. 16;
spectral term: see
term n. 11 d;
spectral type (
Astr.), any of the types used to classify stellar spectra, each being associated with stars of a characteristic range of temperatures and compositions and designated by a letter or letters.
| 1862 Amer. Jrnl. Sci. Nov. 404 There are few branches of science which promise more magnificent results than the *spectral analysis. 1888 Phil. Mag. XXV. 343 (heading) Mathematical spectral analysis of magnesium and carbon. 1930 Proc. IRE XVIII. 1199 Expression (9) lends itself to spectral analysis into its component frequencies by the following process. 1978 Nature 16 Mar. 232/2 As a further step, we carried out a spectral analysis according to the techniques of Blackman and Tukey on the time series for each of our latitude bands. |
| 1956 Observatory LXXVI. 181 The usual terminology is adopted, where the flux density S from a discrete source refers to the flux in both polarizations, and the *spectral index x refers to the index in the relationship S ∝ (frequency)x. 1967 Astrophysical Jrnl. CL. 5 The average spectral index of twenty-six spirals between 40 and 21 cm is -0·83. 1974 Nature 4 Oct. 398/2 The spectral shape of the pulsed emission..can be approximated by a power law with an energy spectral index of α ∼ 1 to about a GeV. |
| 1900 Sci. Abstr. III. 465 A most useful review of the present state of knowledge respecting *spectral series. 1974 G. Reece tr. Hund's Hist. Quantum Theory iv. 61 Several attempts were made to give a theoretical interpretation of the spectral series. |
| 1890 A. M. Clerke System of Stars iii. 37 About eleven-twelfths of all the stars show linear spectra of absorption. They fall into two great divisions, corresponding to Father Secchi's first and second *spectral types. 1924 Proc. Amer. Acad. Arts & Sci. LIX. 217 If the stellar density for any spectral type were uniform throughout space, the number of stars visible should double with every increase of half a magnitude in brightness. 1973 Smith & Jacobs Introd. Astron. & Astrophysics x. 268 Since we will have occasion to refer to specific spectral types in the following paragraphs, we give the spectral sequence from hot to cool stars (40,000 K to 3000 K) here: O, B, A, F, G, K, and M. Each spectral class is further divided into ten sub⁓classes 0 to 9. |
Hence
ˈspectralism, a spectral or ghostly scene.
specˈtrality, a phantasm; ghostliness.
ˈspectralness, the quality or character of being spectral.
| 1851 Carlyle in New Rev. (1891) Oct. 299 All dreamlike, one *spectralism succeeding another. |
| 1850 ― Latter-d. Pamph. i. 50 Traditions now really about extinct;.. still haunting with their *spectralities..almost all of us! 1880 Scribner's Mag. July 326 There is about it a certain vagueness and spectrality. |
| 1892 W. W. Peyton Memorab. Jesus x. 285 A *spectralness, which..gives you an idea of weirdness. |