| 释义 |
umbral, a.|ˈʌmbrəl|
[f. umbra1 + -al1.]
1. Algebra. Based on the use of umbræ in notation; consisting of umbræ.
1851Sylvester in Lond. etc. Phil. Mag. Apr. 297 My system of umbral or biliteral notation. 1852― in Cambr. & Dubl. Math. Jrnl. VII. 78 note, The umbral method of denoting such a function. 1893Cayley Math. Papers (1897) XIII. 306 It does not appear that there is any monomial umbral expression for the last-mentioned form.
2. Astr. Pertaining to the umbra of sun-spots or eclipses.
1867–77G. F. Chambers Astron. 7 note, The umbral structure [of a sun-spot] is quite complete, and made up of sunken banks of filaments. 1879Newcomb & Holden Astron. 286 The observations consisted in measuring the relative amounts of umbral, penumbral, and photospheric radiation. 1885A. M. Clerke Pop. Hist. Astron. 201 Vapours which are dispersed over the unbroken solar surface are accumulated in the umbral cavity.
3. Geol. The special designation of a series of rocks occurring in Pennsylvania.
1858H. D. Rogers Geol. Pennsylv. I. 144 The Umbral Series contains, in Pennsylvania, but one formation—the Umbral Red Shale... Its prevailing character, which is that of a dark-brownish red shale and red sandstone, it steadily maintains throughout its range.
Hence ˈumbrally adv.
1852Sylvester in Cambr. & Dubl. Math. Jrnl. VII. 87 Express H umbrally under the form [etc.]. 1853― in Phil. Trans. CXLIII. 429 The determinants thus umbrally represented. |