Opening remarks.
IN consecution of this fascinating subject, we will now follow the period of 1844, the date of the "Cycle," by flint of 1860, the year in which the Hartwell Continuation appeared; after a further advertence to most of its matter, and considerable correspondence on the several points connected therewith. It has been suggested to me that some colours may undergo pulsations, but the adduced instances are mostly at low altitudes, where atmospheric influences are prevalent; and there may be a want of rigorous correction of the residual spectra of the refracting telescope. But embarrassments in the outset of any enterprize only enhance the value of proven examples.
It may be noted - en passant - that a slight perturbation
pervaded the minds of observing neophytes on the averment
pronouncing that there are only three primary colours,
namely - red, yellow, and blue; and that the other four -
orange, green, indigo, and violet - are de facto, to
produced by combinations of the former, and are therefore
secondary or compound colours. This is, however,
comparatively easy, as well to suggest as to adopt; but
when an arrogant Goethe - unversed even in first principles
- steps forward in the pride and panoply of popularity to
explain the physiological and chemical qualities of the
same, in order to demolish the “nauseous precepts of
Newton,” we are really taken aback by his temerarious
effrontery. Only think, that because the artists in mosaic
at Rome are said to employ 15,000 varieties of hues - each
of which has 50 shades from the darkest to the lightest -
he would saddle us with 750,000 different tints; and be it
[*23] observed, the workmen in
mosaic use opaque colours only. The intellectual giant had
no business to go beyond his proper literary bounds, and
poach upon science.
In now resuming our theme, we will submit a reprint, with
increment, of the VIIth Chapter of the -
SPECULUM HARTWELLIAN. |
First the flaming red Sprung vivid forth; |
The Sestini Comparisons.
In the Cycle of Celestial Objects (vol. i. page 300-4) I have dwelt generally upon the colours of double stars; and in the Bedford Catalogue, which forms the second volume of this work, have assigned such colours to all the objects as struck me at the time of observation. It seems that towards the close of the labours of Signor Benedict Sestini, of Rome, on a very extensive catalogue of stars, my book reached his hands, and led him to form the table which he has appended to his volume, [4] in hopes that the colours of stars may be more strictly watched. The conclusions which he had arrived at were, that of two thousand five hundred and forty stars (those of Baily’s Catalogue observed at Rome) the yellow stars are about half the total number, and equally distributed; the white stars are one-fifth, in scattered portions; and the orange rather more than one-fifth. The red and the blue are rare from the Pole to 30° of north declination; the blue then become numerous (=1/7) to the Equator, especially from [*24] AR 18h to 20h; and the red abound from 0° to 30° south declination, and AR 16h to 20h.
Sestini’s method.
On Signor Sestini’s instituting the comparisons which he described in his work, he carefully recorded the dates, as a step to ascertaining whether the colours may or may not be found to vary with time. Political furor - a deadly foe to science - drove De Vico, Sestini, and other distinguished members of the Collegio Romano, from their country; and the two former sought and found an asylum in America. In passing through London, Professor De Vico had given me notice of the use to which my Cycle had been applied; and I afterwards received a copy of Sestini’s work, with the following letter from the worthy author in English, dated George-town College, March 19th, 1849:
Soon after I had completed this collection of observations, I conceived the design of sending a copy to you, not only as a mark of respectful esteem, but also from having profiled by your Celestial Cycle in the arrangement and comparison of the observations that I myself had made in the Observatory of the Roman College. But the unmerited expulsion and exile that I and my brethren have suffered, have obliged me to leave almost everything, and the printed copies of the little Memoria remained in the printer’s hands, where I think they are yet. Luckily, a while ago I found a few copies in a trunk, sent to me after the death of our dear De Vico. Therefore I send you now what I could not send you before, and at the same time, and without troubling you, I would desire to know what you advise upon this sort of observations. And, as I have the same objective glass of Cauchoix that I have used in Rome to collect these observations, I desire to know if you approve a review, not entirely but sufficiently general in order to examine if the difference of the climate have any influence on the colour of stars. You can also, if you please, suggest more advisable means than those I have adopted, and I should be very happy if the opportunity of having the same and so good an objective glass that I have used for ten years in Italy could give me the means of lending some advantage to the science: what so sincere a lover of this beautiful science as you are can easily find. On another occasion, and when I become better acquainted with the English language, I hope to thank you for all your favours and kindness. Then also will I tell something of the new observatory of this George-town College, erected and very well furnished by the care of H. Curley, a very able and industrious professor, my colleague.
The observations made and published with my first Memoria are reprinted and collected together with all the others of this second Memoria. [*25] Nevertheless, if I had here a copy, I would join to the second. and I would send both to you.
In reply to Signor Sestini, I expressed my satisfaction with the course of his inquiries, as they might yet be of great value in a very interesting branch of physical phenomena. He should, however, remember that the colours recorded in the Cycle were frequently noted after the eye was fatigued and biassed by previous working in an illuminated field, and reading minute divisions on graduated micrometer-circles. There were also the imperfections of the sight, the materials of the object-glass, and the various atmospheric media to be considered before any crucial exactness could be expected; but that still, under every objection, approaches to satisfactory conclusions must inevitably follow stricter attention to the subject. I therefore recommended occasional references to the heavens for this object only, with the eye kept in sharp order for the purpose, having carefully tested the capacity of that organ in strictly identifying the several gradations of colour. Many of the tints of stellar companions would of course turn out to be merely complementary contrasts; but the inherent colours would become additionally valuable, as strict observation upon them, under efficient means, advanced. Indeed, I added, it may be considered as fully proved, that the hue of some stars is not the effect of contrast, but a physical reality. [5]
Death of De Vico.
The unfortunate exiles - De Vico and Sestini - obtained a
refuge in George-town, on the banks of the Potomac, in the
United States; hoping for employment in the newly-erected
observatory there. Shortly afterwards, in furtherance of
instruments and other scientific objects, the former
recrossed the Atlantic Ocean; but, worn with fatigue and
anxiety of mind, he died in London on the 15th of November,
1848. [*26]
Though usually known as a successful comet-hunter, De Vice
was alive to all other branches of celestial research; and
he had promised me that, whenever opportunity offered, he
would follow up “i colori insigni delle
stelle.”
Ladies' aid called in.
The question is pregnant with interest; and, considering
that it may be advantageously encountered by any diligent,
sharp-sighted amateur who, possessed of a good telescope
and inclined only to easy and pleasing work, is
nevertheless zealous to become useful in the cause of
knowledge, I have herewith subjoined the list of chromatic
comparisons or Sestini's observations with mine; to which
are added those colours which I have since noted at
Hartwell. Several of them were confirmed in direct
comparison by Dr. Lee; it was an occasion on which the eyes
or ladies also were prized, and the tints were mostly
pronounced without reference to the older records.
Here follow the details :-
STAR | Cycle | † | SMYTH | † | SESTINI | † | † | SMYTH | † | † |
† | No. | Epoch | A | B | Epoch | A | B | Epoch | A | B |
35 Piscium | 7 | 1837.9 | Pale white | Violet | 1844.8 | Yellowish | Azure | 1850.7 | White | Purplish |
13 P O Ceti | 17 | 1832.8 | Cream yellow | Small Blue | 1845.8 | Yellowish | Azure | 1849.7 | Yellowish | Fine Blue |
146 P O Ceti | 23 | 1837.9 | Pale topaz | Violet | 1845.8 | Orange Yellow | Dull azure | 1849.7 | Yellow | Flushed blue |
η Casseopeiae | 29 | 1843.2 | Pale white | Purple | 1845.6 | Yellow | Orange | 1850.6 | Dull white | Lilac |
65 Piscium | 31 | 1838.2 | Pure yellow | Pale yellow | 1844.8 | Yellowish | Azure | 1850.8 | Pale yellow | Pale yellow |
Psi Piscium | 37 | 1833.9 | Silvery White | Silvery White | 1845.8 | Fine Azure | Fine Azure | 1849.7 | Flushed white | Pale White |
α Ursa Minoris | 44 | 1838.2 | Topaz yellow | Pale white | 1843.6 | Yellowish | Azure | 1849.6 | Yellow | Dull white |
ζ Piscium | 47 | 1839.0 | Silver-White | Pale grey | 1844.8 | Yellowish | Dingy yellow | 1849.7 | White | Greyish |
37 Ceti | 48 | 1838.9 | White | Light Blue | 1844.8 | Yellow | White | 1849.7 | Cream white | Dusky |
ψ Casseopeiae | 52 | 1836.3 | Orange tint | Blue | 1844.8 | White | White | 1850.2 | Golden yellow | Ash coloured |
83 P.I Piscium | 54 | 1837.0 | Yellow | Pale blue | 1844.8 | Yellow | Pale Azure | 1855.4 | Pale yellow | Bluish |
γ Arietis | 72 | 1837.9 | Bright white | Pale grey | 1844.9 | White | White | 1850.7 | Full white | Faint Blue |
λ Arietis [*27] | 79 | 1830.9 | Yellowish-white | Blue | 1844.9 | White | Pale azure | 1857.7 | Faint blue | Flushed blue |
α Piscium | 81 | 1835.9 | Pale green | Blue | 1844.8 | White | White | 1850.8 | Greenish | Pale blue |
γ Andromedæ | 82 | 1843.3 | Orange | Emerald Green | 1846.5 | Red orange | Lighter red | 1850.3 | Deep Yellow | Sea Green |
14 Arietis | 86 | 1833.9 | White | Blue | 1844.9 | Yellowish | Bluish white | 1857.7 | Pale white | Grey |
72 P.II Casseopeiae | 97 | 1834.8 | Pale yellow | Lilac | 1845.6 | White | White | 1857.7 | Yellowish white | Purplish |
θ Persei | 109 | 1833.6 | Yellow | Violet | 1845.6 | Red orange | Lighter red | 1849.6 | Yellow | Dusky blue |
π Persei | 115 | 1838.8 | Orange | Smalt blue | 1845.7 | Golden orange | Azure | 1850.7 | Reddish yellow | Blue |
32 Eridani | 147 | 1843.2 | Topaz yellow | Sea-green | 1845.9 | Yellow | White | 1850.3 | Bright yellow | Flushed Blue |
φ Tauri | 158 | 1832.8 | Light Red | Cerulean Blue | 1845.8 | Golden orange | Azure | 1852.5 | Pale red | Blue |
χ Tauri | 160 | 1831.9 | White | Pale sky blue | 1815.8 | White | Azure | 1850.7 | White | Grey |
62 Tauri | 161 | 1835.9 | Silver white | Purple | 1845.8 | White | White | 1850.7 | White | Pale purple |
88 Tauri | 169 | 1832.9 | Bluish white | Cerulean Blue | 1845.8 | White | White | 1852.5 | Bluish white | Blue |
τ Tauri | 171 | 1831.9 | Bluish white | Lilac | 1845.8 | Very white | Azure | 1852.5 | Pale white | Violet |
ω Aurigae | 174 | 1833.8 | Pale Red | Light Blue | 18457 | White | White | 1850.7 | Flushed white | Light blue |
62 Eridani | 175 | 1831.9 | White | Lilac | 1845.9 | Light yellow | Azure | 1852.5 | Pale white | Flushed blue |
14 Aurigae | 188 | 1832.8 | Pale Yellow | Orange | 1845.7 | White | Azure | 1850.7 | Greenish yellow | Bluish yellow |
23 Orionis | 197 | 1835.2 | White | Pale grey | 1845.9 | Yellowish | Bluish white | 1850.2 | Creamy white | Light blue |
111 Tauri | 198 | 1832.9 | White | Lilac | 1845.9 | Yellowish | White | 1857.7 | Pale white | Lilac |
118 Tauri | 205 | 1838.9 | White | Pale blue | 1845.9 | White | White | 1850.2 | White | Bluish |
δ Orionis | 211 | 1935.1 | Brillant white | Pale violet | 1843.9 | Yellowish | Very white | 1850.2 | Pale white | Flushed white |
λ Orionis | 215 | 1813.1 | Pale white | Violet | 1843.9 | Yellowish | Bluish white | 1850.2 | Pale yellow | Purplish |
ι Orionis | 218 | 1832.1 | White | Pale blue | 1843.9 | White | Pale blue | 1852.5 | Pale white | Bluish |
26 Aurigae | 220 | 1833.1 | Pale white | Violet | 1845.7 | Yellowish | Blue | 1849.7 | Deep blue | Pale blue |
σ Orionis | 222 | 1832.2 | Bright white | Bluish | 1843.9 | Yellow | Azure | 1850.3 | White | Grey |
ζ Orionis | 223 | 1839.2 | Topaz yellow | Light purple | 1843.9 | Yellowish | Azure | 1850.3 | Yellow | Flushed blue |
γ Leporis | 225 | 1832.1 | Light yellow | Pale green | 1843.9 | Orange yellow | Orange red | 1852.2 | Pale yellow | Flushed |
8 Moncerotis [*28] | 245 | 18342 | Golden yellow | Lilac | 1845.9 | Pale yellow | Yellowish | 1850.8 | Yellow | Flushed blue |
15 Geminorum | 247 | 1832.0 | Flushed white | Bluish | 1845.9 | Orange | Yellowish | 1852.4 | Pale white | Ash coloured |
20 Geminorum | 252 | 1834.0 | Topaz yellow | Cerulean blue | 1815.9 | Yellowish orange | Yellow | 1849.7 | Yellow | Pale blue |
π2 Canis Majoris | 270 | 1834.1 | Flushed white | Ruddy | 1845.9 | Yellowish | Reddish | 1851.3 | Bluish white | Ruddy |
α Geminorum | 292 | 1843.1 | Bright white | Pale white | 1845.9 | Yellowish | Yellow | 1849-2 | Very white | Pale white |
ζ Cancri | 315 | 1813.1 | Yellow | Orange tinge | 18460 | Yellow | White | 1849.2 | Yellow | Bright Yellow |
φ2 Cancri | 320 | 1813.2 | Silvery white | Silvery White | 1846.0 | Yellowish | White | 1819.2 | White | Pale white |
υ1 Cancri | 321 | 1848.2 | Pale white | Greyish | 1846.0 | White | White | 1819.2 | White | Dusky white |
72 P.VIII Argo Navis | 323 | 1830.8 | Red | Green | 1846.1 | Orange red | Yellowish | 1851.3 | Orange | Bluish green |
108 P.VIII Hydrae | 326 | 1839.1 | Pale yellow | Rose tint | 1846.0 | Orange | Orange | 1849.2 | Full yellow | Flushed |
ι Cancri | 336 | 1836.2 | Pale orange | Clear blue | 1846.0 | Fine orange | Azure | 1851.3 | Dusky orange | Sapphire blue |
τ1 Hydrae | 360 | 1831.9 | Flushed white | Lilac | 1846.1 | Yellow | Yellow | 1851.3 | Pale white | Dusky |
6 Leonis | 363 | 1832.2 | Pale rose tint | Purple | 1846.0 | Fine orange | White | 1851.3 | Flushed yellow | Pale purple |
7 Leonis | 364 | 1832.2 | Flushed white | Violet tint | 1846.0 | Rother blue | White | 1851.3 | Bluish white | Pale violet |
9 Sextantis | 371 | 1832.2 | Blue | Blue | 1846.0 | Dingy orange | Dingy orange | 1851.3 | Flushed blue | Pale blue |
33 Sextantis | 384 | 1839.1 | Topaz yellow | Smalt blue | 1816.1 | Pale yellow | Pale yellow | 1851.2 | Rich yellow | Ceruleau blue |
54 Leonis | 391 | 1839.3 | White | Grey | 1846.0 | Yellow | White | 1851.3 | Silvery white | Ash coloured |
Phi Leonis | 405 | 1831.2 | Pale yellow | Violet | 1846.2 | Pale yellow | White | 1851.3 | Pale yellow | Dusky red |
90 Leonis | 421 | 1835.4 | Silvery white | Purplish | 1846.1 | White | White | 1851.3 | Silver white | Pale purple |
δ Corvi | 446 | 1831.3 | Pale yellow | Purple | 1846.3 | Slightly yellow | White | 1851.3 | Light yellow | Purple |
24 Coma Berencis | 451 | 1836.1 | Orange colour | Emerald tint | 1844.4 | Gold | Azure | 1851.3 | Orange | Lilac |
143 P.XII. Virginis | 453 | 1833.3 | Pale yellow | Greenish | 1846.3 | Red | Azure | 1851.3 | Yellowish | Flushed blue |
12 Canum Venaticorum | 466 | 1837.4 | Flushed white | Pale blue | 1844.5 | Yellowish | Blue | 1850.5 | Full white | Very pale |
ζ Ursa Majoris | 480 | 1839.3 | Brilliant white | Pale emerald | 1841.5 | White | Yellowish | 1819.2 | White | Pale green |
ι Boötis [*28] | 508 | 1838.2 | Pale yellow | Creamy | 1844.5 | Orange yellow | Azure | 1850.6 | Light yellow | Dusky white |
π Bootis | 517 | 1836.5 | White | White | 1844.4 | Yellow | Less yellow | 1850.6 | White | Creamy |
10 Hydrae | 519 | 1831.5 | Pale orange | Violet tint | 1846.4 | Yellow | Yellowish | 1851.4 | Deep yellow | Reddish violet |
212 P.XIV. Librae | 524 | 1833.4 | Straw colour | Yellow | 1846.3 | Orange | Orange | 1851.4 | Yellow | Dusky |
44 Boötis | 529 | 1842.5 | Pale white | Lucid grey | 1844.5 | Orange | Orange | 1858 6 | Pale yellow | Dusky |
δ Boötis | 537 | 1835.5 | Pale yellow | Light blue | 1844.5 | Gold yellow | Yellowish azure | 1851.3 | Yellow | Lilac |
μ1 Boötis | 542 | 1832.3 | Flushed white | Greenish white | 1844.5 | Yellow | Yellowish azure | 1860.6 | Yellowish | Greenish white |
ζ Corona Borealis | 549 | 1842.6 | Bluish white | Smalt blue | 1844.5 | White | White | 1850.6 | Flushed white | Bluish green |
54 Librae | 558 | 1842.5 | Bright white | Pale yellow | 1844.4 | Orange | Orange | 1850.6 | Creamy white | Pale yellow |
β Scorpii | 559 | 1833.4 | Pale white | Lilac tinge | 1846.4 | Yellow | Whitish | 1851.4 | Yellowish white | Pale blue |
κ1 Herculis | 560 | 1835.4 | Light yellow | Pale garnet | 1844.5 | Yellow | Orange | 1851.3 | Pale yellow | Reddish yellow |
ν Scorpii | 561 | 1831.5 | Bright white | Pale lilac | 1846.5 | Yellowish | White | 1850.6 | Pale yellow | Dusky |
σ Scorpii | 568 | 1838.3 | Creamy white | Lilac tint | 1846.5 | Yellow | White | 1851.4 | Dusky white | Plum colour |
236 P.XVI Scorpii | 593 | 1833.4 | Yellowish white | Pale green | 1845.5 | Yellow | White | 1851.4 | Creamy white | Greenish |
μ Draconis | 602 | 1839.5 | White | White | 1844.5 | Yellow | Azure | 1850.7 | White | Pale white |
36 Ophiuchi | 604 | 1842.4 | Ruddy | Pale yellow | 1846.5 | Orange | Yellow | 1851.4 | Ruddy tint | Yellowish |
39 Ophiuchi | 607 | 1838.5 | Pale orange | Blue | 1846.5 | Orange | Yellow | 1851.4 | Pale orange | Bluish |
ν Serpentis | 610 | 1832.6 | Pale sea green | Lilac | 1846.5 | Yellow | Red | 1851.4 | Silvery tint | Native copper |
ρ Herculis | 613 | 1839.7 | Bluish white | Pale emerald | 1844.4 | Yellow | Deeper yellow | 1850.5 | Greyish | Greenish |
53 Ophiuchi | 618 | 1836.5 | Bluish | Bluish | 1844.5 | Bluish | Bluish | 1850.5 | Greyish | Pale blue |
95 Herculis | 631 | 1838.8 | Greenish | Cherry red | 1844.5 | Gold yellow | Gold yellow | 1851.3 | Pale green | Reddish |
70 Ophiuchi | 633 | 1842.5 | Pale topaz | Violet | 1845.9 | Fine orange | Copper colour | 1849.5 | Topaz yellow | Purplish |
ω Draconis | 672 | 1837.9 | Orange yellow | Lilac | 1844.5 | Reddish | Red orange | 1851.3 | Orange | Lilac |
15 Aquliae | 678 | 1831.6 | White | Lilac tint | 1846.5 | White | Yellow | 1851.4 | Yellowish white | Red lilac |
28 Aquilae | 699 | 1831.4 | Pale white | Deep blue | 1844.5 | White | Yellowish | 1851.4 | Dusky white | Lilac blue |
β Cygni | 700 | 1837.6 | Topaz yellow | Sapphire blue | 1844.5 | Orange gold | Azure | 1849.6 | Golden yellow | Smalt blue |
ε Sagittae [*30] | 704 | 1833.8 | Pale white | Light blue | 1844.5 | Yellow | Bluish yellow | 1850.6 | Faint yellow | Bluish |
54 Sagittarii | 705 | 1837.6 | Yellow | Violet | 1845.5 | Orange | White | 1850.7 | Yellow | Pale Lilac |
ζ Sagittae | 718 | 1838.6 | Silvery white | Blue | 1844.5 | Yellowish white | Azure | 1850.6 | Flushed White | Cerulean blue |
56 Aquilae | 722 | 1834.6 | Deep yellow | Pale blue | 1846.5 | Yelllow | Yellow | 1850.6 | Yellow | Bluish |
κ Cephei | 743 | 1838.8 | Bright white | Smalt blue | 1844.6 | Yellowish | Azure | 1851.3 | Pale yellow | Blue |
γ Delphni | 769 | 1839.7 | Yellow | Light emerald | 1844.5 | Orange | Yellow | 1850.7 | Golden yellow | Flushed grey |
ε Equulei | 770 | 1838.8 | White | Lilac | 1844.5 | Gold orange | Azure | 1551.4 | Pale yellow | Bluish lilac |
1 Pegasi | 782 | 1833.9 | Pale orange | Purplish | 1844.5 | Orange | Azure | 1851.4 | Deep yellow | Lilac blue |
β Cephei | 789 | 1843.1 | White | Blue | 1844.6 | White | White | 1851.3 | Yellowish | Flushed blue |
3 Pegasi | 790 | 1837.8 | White | Pale blue | 1844.5 | White | Yellow | 1850.5 | Flushed white | Greyish |
ε Pegasi | 794 | 1833.6 | Yellow | Blue | 1844.5 | Gold yellow | Azure | 1851.4 | Bright yellow | Blue lilac |
μ Cygni | 795 | 1839.6 | White | Blue | 1841.5 | Yellow | More yellow | 1850.6 | White | Pale blue |
29 Aquarii | 800 | 1830.8 | Brilliant white | White | 1846.5 | Red orange | Same. lighter | 1852.7 | White | Bluish |
χ Cephei | 809 | 1839.6 | Bluish | Bluish | 1844.6 | White | Yellowish | 1851.4 | Flushed | Pale blue |
ζ Aquarii | 813 | 1812.6 | Very white | White | 1845.8 | Orange yellow | Pale yellow | 1859.2 | Flushed white | Creamy |
δ Cephei | 815 | 1837.7 | Orange tint | Fine blue | 1841.8 | Orange | Azure | 1819.2 | Deep yellow | Ceruleau blue |
τ1 Aquarii | 822 | 1838.7 | White | Pale garnet | 1845.5 | White | Azure | 1819.2 | Pale white | Flushed |
ψ Aquarii | 833 | 1834.9 | Orange tint | Sky blue | 1845.8 | Gold | Azure | 1850.8 | Topaz yellow | Ceruleau blue |
94 Aquarii | 834 | 1838.9 | Pale rose tint | Light emerald | 1845.8 | Orange yellow | Orange | 1850.5 | Orange tint | Flushed blue |
101 P.XXIII. Casseopeiae | 839 | 1830.9 | Light yellow | White | 1845.6 | White | Yellowish | 1852.7 | Pale white | Yellowish |
107 Aquarii | 844 | 1832.8 | Bright white | Blue | 1845.8 | Yellowish white | Yellowish | 1850.7 | White | Purplish |
Anomalies. [*31]
All the differences in the above list are subject to several doubts, and many of the records hae been noted without a very strict attention to the question. In the Cycle, the main disagreements arc mentioned between the tints of stars as given by Sir William Herschel and myself; and the anomaly is partly accounted for by his peculiarity of vision, and partly by the composition of metal in his reflectors. But I am at a loss why refractors should differ so widely as here shown ; and therefore hope the subject will be more closely pursued than it has hitherto seen. We are aware that the notations independently made at various epochs will vary in term, though to the observers mind they may mean nearly the same tint, still some of the differences mentioned by Signor Sestini in his interesting Memoir arc singularly striking. He says - “Now, beginning with the companion of γ Andromedæ, we have Smyth emerald-green and Sestini white; but Herschel and Struve at another date call it azure. Moreover, observing it again after a lapse of two years, and four years after Smyth, I find it no longer white, but a strong blue !” And again - now see B (95) Herculis ; according to Smyth, one greenish and the other red ; but we think them both golden yellow. A Ophiuchi, by Smyth, one ruddy and the other pale yellow, but we both take them as being orange. The contrary occurs in ι Boötis, the components of which by Smyth are both pale yellow; but we deem one to be orange and the other azure.
Sir David Brewster’s Experiment.
Under the circumstances already alluded to, I am not at this stage disposed to theorise on the objects thus brought into juxta-position: and the colours of double-stars must be much more accurately assigned, and more ably experimented upon, before we can really admit that the nature and character of those suns do actually change in short periods. Sir David Brewster observes, that there can be no doubt that in the spectrum of every coloured star certain rays are wanting which exist in the solar spectrum; but have no reason to believe that the absent rays are absorbed by any atmosphere through [*32] which they pass. And in recording the only observation perhaps yet made to analyse the light of the coloured stars, he says :- “ In the orange-coloured star of the double-star ζ Herculis, I have observed that there are several defective bands. By applying a fine rock-salt prism, with the largest possible refracting angle. to this orange-star, as see in Sir James South's great achromatic refractor, its spectrum had the annexed appearance (in the Campden Hill Journal), clearly showing that there was one defective band in the red space, and two or more in the blue space. Hence the colour of the star was orange, because there was a greater defect of blue than of red rays.” This instance shows, that an approximation by instrumental means to the spectra of the brighter stars ought not to be despaired of ; and that prospect should not admit of any relaxation in our present motive call.
Teneriffe Experiment.
In the year 1856, on my son’s going to the island of
Teneriffe to make his “Astronomical
Experiment,” it occurred to me that it would be a
singularly fine opportunity to test sidereal polychromy;
since it would be marked by a spot where some thousands of
feet of the grossest portion of the atmosphere are
eliminated.
This meritorious expedition, which “at once
converted into an actual and successful tact a theoretical
idea, long thought well of, but never previously carried
into practice,” may be recognized as the foundation
of the of the branch so appropriately designated Mountain
Astronomy. Indeed the advantages of elevated stations are
sufficiently obvious to countenance the hope of reaping,
thereby, results of the utmost importance to knowledge.
Newton himself sounded a tocsin to this effect, in
asserting that telescopes “cannot be so termed as to
take away that conclusion of rays which arises from the
tremors of the atmosphere. The only remedy is a most serene
and quiet air, such as may perhaps be found on the tops, of
the highest mountains above the grosser clouds.” It
was under a conviction of this truth - and having a
personal knowledge of both sites - that I earnestly wished
my friend Lassell his huge equatorial on ætna,
instead of Malta.[*33]
Such being the justifiable expectations of the problem, my
son accordingly scrutinised the following stars from the
“Cycle” for me; they having been chosen out of
those objects which then happened to be in apparition from
the mountain, during his interesting continuance upon it.
The observations were made at two stations: the colours
noted on the 29th of July and 4th of August were examined
with the 5-foot Sheepshanks equatorial, at Guajara, a
height of 8870 feet; and those of September 4th, 5th, and
6th, were made with the Pattinson telescope of 7.25 inches
aperture, and parallactic movement, at the Alta Vista,
where the altitude is 11,000 feet. The following are his
registered results, with comparisons from the "Cycle ;"
Which last are of various dates from 1830 to 1843:-
OBJECTS | TENERIFFE | BEDFORD | ||
JULY 29th. | ||||
α Herculis | A. Cadmium yellow | B. Greenish | A. Orange | B. Emerald, or blue |
39 Ophiuchi | A. Pale yellow | B. Faint blue | A. Pale orange | B. Blueish green |
5 [V?] Serpentis | A. Pale yellow | B. Warm lilac | A. Pale yellow | B. Light grey |
ξ? Herculis | A. White | B. Bluish | A. Blueish white | B. Pale emerald |
95 Herculis | A. White | B. White | A. Light apple green | B. Cherry red |
70 Ophiuchi | A. Pale yellow | B. Greyish | A. Pale topaz | B. Violet |
α Lyrae | A. White | B. Violet | A. Pale sapphire | B. Smalt blue |
AUGUST 4th. | ||||
α Herculis | A. Cadmium yellow | B. Greenish | (as above) | (as above) |
95 Herculis | A. and | B. both yellow with a tinge of bluish green | (as above) | |
70 Ophiuchi | A. Yellow | B. Warm green | (as above) | |
5 Aquilae | A. Pale yellow | B. Bluish C. Blue | A. White | B. Lilac. C. Blue |
28 Aquilae | A. White | B. Blue | A. Pale White | B. Deep blue |
β Cygni | A. Pale yellow | B. Blue | A. Topaz yellow | B. Sapphire blue |
186 Antinoi | A. Yellow | B. Blue | A. Pale white | B. Sky blue |
SEPTEMBER 4th | ||||
α Scorpii | A. Coppery Red | B. Blue | A. Fiery red | B. Pale |
α Herculis | A. Orange | B. Greenish | (as above) | |
ζ Sagittae [*34] | A. Yellow |
B. Blue |
A. Silvery White | B. Blue |
α1 Capricorni | A. Yellow | B. Blue | A. Pale yellow | B. Blue |
1 Pegasi | A. Yellow | B. Blue | A. Pale orange | B. Purplish |
β Cephei | A. White | B. Purple | A. White | B. Blue |
3 Pegasi | A. Whitish | B. Warm grey | A. Pale | B. Pate blue |
ζ Piscium | A. Yellow | B. Grey | A. Silver white | B. Pale grey |
γ Arietis | A. White | B. White | A.Brilliant sapphire | B. Pale grey |
λ Arietis | A. Pale yellow | B. Bright lilac | A. Yellowish | B. Blue |
α Piscium | A. Blue | B. White | A. Pale green | B. Blue |
SEPTEMBER 5th. | ||||
α Aquilae | A. Pale yellow | B. Grey | A. Pale yellow | B. Violet tint |
γ Delphni | A. Cadmium yellow | B. Orange tinge | A. Cadmium yellow | B. Bright emerald |
τ1 Aquarii | A. Light yellow | B. Pale violet | A. White | B. Pale garnet |
α Piscis Australis | A. White | B. Blue | A. Reddish | B. Deep sky blue |
ψ Aquarii | A. Cadmium yellow | B. Blue | A. Orange red | B. Sky blue |
94 Aquarii | A. Yellow | B. Light warm blue | A. Pale rose-tint | B. Light emerald |
101 Casseopeiae | A. Light yellow | B. Grey blue | A. Light yellow | B. Violet |
C. Blue | D. Violet | C. Blue | D. (not noticed) | |
107 Aquarii | A. Pale yellow | B. White | A. Bright yellow | B. Blue |
35 Piscium | A. Yellow | B. Pale violet | A. Pale white | B Violet tint |
113 Ceti | A. Rich yellow | B. Warm grey | A. Cream yellow | B. Smalt blue |
γ Arietis | A. Light yellow | B Light yellow | (as above) | |
222 Arietis | A. Grey | B. Blue | A. Topaz yellow | B. Deep blue |
C. Lilac | D. Yellow | C. Lilac | D. Pale blue | |
α Piscium | A. White | B. White | ††(as above) | |
γ Andromedæ | A. Orange | B. and C. Green | A: Orange | B. Emerald green |
32 Eridani | A. Orange | B. Greenish | A. Topaz yellow | B. Sea Green |
SEPTEMBER 6th | ||||
σ Casseopeiae | A. Pale yellow | B. Light blue | A. Flushed white | B. Smalt blue |
35 Piscium | A. Pale yellow | B. Pale lilac | (as above) | |
113 Ceti | A. Yellow | B. Warm grey | (as above) | |
146 Ceti | A. Yellow | B. Pale violet | A. Pale topaz | B. Violet tint |
π Casseopeiae | A. Yellow | B. Indian red | A. Pale white | B. Purple |
65 Piscium | A. White | B. White | A. Pale yellow | B. Pale yellow |
ψ1 Piscium | A. White | B. White | A. Silvery white | B. Silvery White |
ζ Piscium | A. White. | B. Reddish | (as above) |
General discussion of the foregoing list. [*35]
In the preceding list there to be a very general similarity of eye-judgment between my son and myself; whence it would appear that the difference made by 11,000 feet of the lower atmosphere on the colours, is not so great as might have been anticipated. But the most striking and inexplicable difference in the comparison is that of 95 Herculis; for, in the observations at the Peak of Teneriffe, the tints of the two stars - though not quite the same at each examination -were judged to be common to both, and the impression was ratified by the evidence of some Spanish visitors at the astronomical aerie. Not a little taken aback, however; by the unexpected announcement - the more unexpected in consequence of the general agreement which existed throughout the list, even in some of the most delicate hues I took the earliest opportunity of returning to the charge, when there was the A Apple green and B cherry red, as recorded by me nearly a quarter of a century before! To avoid all suspicion of bias I invited my colleagues to the task, and soon received an answer from Mr. Dawes, saying - “On referring to my colour-estimations, I find that they agree very nearly with your own.” Lord Wrottesley pronounced A to be greenish and B reddish in 1857.46; and at the same epoch Mr. Fletcher reported that A, to his eye, was light green and pink ; while to his brother H. A. Fletcher one was bluish green and the other orange, and to Mr. T. W. Carr A was either light blue or green, and B dull red. To add to the perplexity of the instance, Sestini saw them both golden yellow at Rome, in 1844; while his colleague, De Vico, in the memoirs of the “Osservatorio dcl Collegio Romano,” in the same place and with, the same instrument, dubs them “rossa e verde.” Assuredly this is most passing strange, since the means in these cases were pretty equally powerful, and chromatic personal equation-or the faculty in a greater or less degree of appreciating differences of colour, cannot be entitled to consideration with the discrepancies of 95 Herculis.
[4] A selection from these, twenty nine in number, was communicated by the late Professor de Vico to Schumacher at Altona, in Isis; who published the details in Astronomische Nachrichten; No. 684. .
[5] Secchi (Osservatorio del Collegio Romano) says - “Until now a means has been wanting to decide the degree of colour of double stars with precision. If I do not deceive myself I have succeeded, at least to indicate a means by which we can determine it without mistake in centuries to come: this means is derived from the spectrum of the electric spark (questo dallo spectiro della scintilla electrica), and I will shew it in conclusion. My attempts hitherto, for want of time and apparatus, have not been reduced to practice.”