140 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[May, 



adjoining two of vliith correspunils to one minute of time at the equator. 

 The tube and speculum, including the bed on which the latter rests, weigh 

 about 15 tons. 



The telescope rests on an universal joint, placed on masonry about six feet 

 below the grounrl, and is elevated or depressed by a chain and windlass ; and, 

 although it weighs about 15 tons, the instrument is raised by two men with 

 great facility. Of course, it is counterpoised in every direction. 



When completed its range will embrace an arc between 10 degrees of alti- 

 tude towards the south and 47 degrees north ; so that all objects between the 

 pole and 27 degrees south of the equator will be observable with it; whilst in 

 the equator any object can be viewed with it about 40 minutes of time on 

 cither side of the meridian. 



The observer when at work stands in one of four galleries, Ihe three highest 

 of which are drawn out from the western wall, whilst the fourth, nr lowest, 

 has for its base an elevating i>latform, along the horizontal surface of which 

 a gallery slides from wall to wall by machinery wilhin the observer's reach, 

 but which a child may work. 



The telescope lying at its least altitude can be raised to the zenith by the 

 two men at the windlass in sis minutes ; and so manageable is the enormous 

 mass, that give me the riglit ascension and declination of any celestial object 

 between these points, and I will have the object in the field of the telescope 

 within eight minntes from the first attempt to raise it. 



When the observer has found the object, he must at present follow it by 

 rackwork within its reacli. As yet it has no equatorial motion, but it very 

 shortly will, and at no very distant day clockwork will be connected with it, 

 when the observer, if I mistake not, will, whilst observing, be almost as com- 

 fortable as if he were reading at a desk by his fireside. 



The night of the 5lh of March was, 1 think, the finest 1 ever saw in Ireland. 

 Many nebulfe were observed by Lord Rosse, Dr. Robinson, and myself. 

 Most of ihem were, for the first lime since their creation, seen by us as groups 

 or clusters of stars ; whilst some, at least to my eyes, showed no such reso- 

 lution. Never, however, in my life did I see sucli glorious sidereal pictures 

 as this instrument afforded us. 



Although, however, the power of this telescope in resolving nebula: into 

 stars hitherto considered irrcsnlveatle was extremely gratifying, still it was 

 in my mind little more than 1 had anticipated; for experience has long since 

 told me that a telescojie may show nel.ul:e, even those resolvable by it, very 

 well, whilst, when directed to a bright star, with a very moderate magnifying 

 power, its imperfections will be actually otlensive. 



Perfection of figure, then, of a telescope must be tested, not by nebulae, but 

 by its performance on a star of Ihe first magnitude. If it will, under high 

 power, show the star round and free from optical appendages, we may safely 

 enough take it for granted it will not only show nebula2 well, but any other 

 celestial object as it ought. Regulus on the llth being near the meridian, I 

 placed the telescope on it, and with the entire aperture and a magnifying 

 power of 800 I saw, with inexpressible delight, the star free from wings, tails, 

 or optical appendages ; not indeed like a planetary disc, as in my large achro- 

 matic, but as a round image resembling voltaic light between charcoal points ; 

 and so little aberrations had this brilliant image that I could have measured 

 its distance from, and position with, any of the stars in the field with a 

 spider's line micrometer, and a power of 1,000, without the slightest difliculty ; 

 for not only was the large star round, but the tolescoiie, although in the open 

 air and the wind blowing rather fresh, was as steady as a rock. 



On subsequent nights', observations of other nebulx, amounting to some 

 30, or more, removed most of them from the hst of nebulje, where they had 

 long figured, to that of clusters ; whilst some of these latter, but more espe- 

 cially 5 Messier, exhibited a sidereal picture in the telescope such as man be- 

 fore had never seen, and which for its magnificence baffies all description. 



Of the moon a few words must suffice. Its appearance in my large achro- 

 matic, of 12 inches aperture, is known to hundreds of your readers ; let them 

 then imagine that with it they look nt the moon, whilst with Lord Rosse 's 6 

 feet they look into it, and they will not form a very erroneous opinion of the 

 performance of the leviathan. 



On the 15th of March, when the moon was seven days and a half old, I 

 never saw her unillumined disc so beautifully nor her mountains so tempt. 

 Ingly measurable. On my first looking into the telescope, a star of about the 

 7th magnitude was some minutes of a degree distant from the moon's dark 

 limb. Seeing that its occultation by the moon was inevitable, as it was the 

 first occiilation which had been observed w ith that telescope, f was anxious 

 that it should be observed by its noble maker ; and very much do I regret 

 that through kindness towards me he would not accede to my wish ; for the 

 star, instead of disappearing the moment the moon's edge came in contact 

 with it, apparently glided on the moon's dark face, as if it had been seen 

 through a transparent moon, or as if the star were between me and the moon. 

 It remained on the moon's disc nearly two seconds of time, and then instantly 

 disappeared, at lOh. 9m. 5y-72s. sidereal time. I have seen this apparent 

 projeclion of a star on the moon's face several times, but from the great 



brilliancy of Ihe star this was the most beautiful I ever saw. The cause of 

 this phenomenon is involved in impenetrable mystery.' 



The only telescopes in point of size comparable with Lord Rosse's 3 feet 

 and 6 feet, are Sir William Herschcl's 20 feet and 40 feet Lemairean's. The 

 20 feet had a speculum of 18 8 inches diameter, and the 40 feet one of 4 feet, t 



The Lomaireau of 18'8 inches diameter in point of light is equal to a New- 

 tonian of 22 inches and a half diameter. 



The Limairean of 4 feet diameter is equal to a Newtonian of 57 inches and 

 4 tenths. 



The Lemairean of 3 feet is equal to a Newtonian of 43 inches. 



And the Lemairean of C feet is equal to a Newtonian of 86 inches. 



By substituting then the Lemairean form for the Newtonian, the present 3 

 feet Newtonian will be made as effective as if it were 43 inches diameter, and 

 the 6 feet as if it w ere 86 inches in diameter ; or the quantity of light in each 

 telescope, after the alteration, will be, to its present light, as 7 to 5 nearly, or 

 almost half as much again as it now has. 



Seeing, then, that the change from the Newtonian to the Lemairean con- 

 struction will be attended with such an accession of light. Lord Rosse, having 

 determined geometrically the form of the curve requisite to produce with it a 

 definition of objects equal to that which each of the telescopes at present 

 gives, is devising mechanical means for producing it ; but, as he is in about a 

 fortnight coming over to England to attend his parliamentary duties, it is 

 probable that this important desideratum will scarcely be effected till autumn 

 cnmcs upon us. 



What will be the power of this telescope when it has its Lemairean form u 

 is not easy to divine ; — what nebulte will it resolve into stars ; in what nebula: 

 will it not find stars; — how many satellites of Saturn will it show us; 

 — how many will it indicate as appertaining to Uran'js ;— how many nebula: 

 never yet seen by mortal eye will it present to us; — what spots will it show 

 us on the various planets; will it tell us what causes the variable brightness 

 of many of the fixed stars ;— will it give us any information as to the consti- 

 tution of the planetary nebulic ; — will it exhibit to us any satellites encircling 

 them ; — will it tell us why the satellites of .Tupiler, which generally pass over 

 Jupiter's face as discs of nearly white light, sometimes traverse it as black 

 patches ; — will it add to our knowledge of the physical construction of nebu- 

 lous stars ; — of that mysterious class of bodies which surround some stars, 

 called, for want of a better name, " photospheres ;'" — will it show the annular 

 nebula of Lyra merely as a brilliant luminous ring, or will it exhibit it as 

 thousands of stars arranged in all the symmetry of an ellipse ; — will it enable 

 us to comprehend the hitherto incomprehensible nature and origin of thelight 

 of the great nebula of Orion : — will it give us in easily appreciable quantity 

 the parallax of some of the fixed stars, or will it make sensible to us the 

 parallax of the nebula: themselves; — finally, having presented to us original 

 portraits of the moon and of the sidereal heavens, such as man has never 

 dared even to anticipate, — will it by daguerreotypic aid administer to us cop'es 

 founded upon truth, and enable astronomers of future ages to compare the 

 moon and heavens as they then may be, with the moon and heavens as they 

 were? Some of these questions will be answered affirmatively, others nega- 

 tively, and that, too, very shortly ; for the noble maker of the noblest instru- 

 ment ever formed by man " has cast his bread upon the waters, and « ill, with 

 God'.s blessing, find it before many days." 



* Would not tliis appearance, it is aslced witli great submission, indicate a refracting 

 atmosptiere which the telescopes hitherto constructed have not been aljle to detect? If 

 this hypothesis turn out correct, it will be easy enough to determine the extent of the 

 atmosphere, by observing in sidereal occultations the time of a star's passing from ths 

 moon's apparent edge (namely, the limits of her atmosphere), to her real edge. Since 

 the above was written, a letter from Sir James South has appeared in the Times, in which 

 it is stated that the phenomenon occurs both at immersion and emersion. Is not this a 

 powerful conlirmation of our hypothesis ? — Ed. C. E. and A, Journal. 



t Sir James South intends here, we presume, to draw a comparison between 'reflect* 

 ing' telescopes only. 



Arcititecturai, Novelty. — The new theatre which is building at Livorno, 

 ' Anglice' Leghorn, will differ altogether from any othet structure of the kind, inasmuch 

 as it will be available for performances by daylight as well as of an evening, since instead 

 of the usual ceiling, the auditory, i. e., the pit or portion surrounded by stage and boxes, 

 will be covered by an open glazed dome. Ingenious as seems the idea — whose we are not 

 informed, the architect's name being as usual suppressed, — and singular as will be the 

 effect, it may be questioned whether it will be found any improvement upon the present 

 system, but rather a sort of • amphibious ' contrivance, neither tish nor rtesh, nor parti- 

 cularly advantageous for either day-time or evening. If the morning performances are to 

 he merely concerts daylight will suit well enough, but not for dramatic representations 

 vfith scenery and dresses, if only because the stage itself would be in obscurity compared 

 with the rest of the house, unless it were to be lighted up as usual by " foot-lamps," and 

 from the wings, in which case the mi.\ture of daylight and artilicial light together would 

 be e-tceedingly disagreeable. Again, has the effect then attending a large domed skylight 

 been well coasidered for evening exhibitions > At such times, it must show only as a dark 

 void over-head, except perhaps of a fine moonlight night, when Madam Luna could peep 

 in from above upon the spectators and the performances. To render it ornamental and 

 architecturally effective, the dome ought to be glazed with coloured glass — either diapered 

 or p!ain — and lit up externally, within a space for the purpose, between the dome and 

 outer roof ; or perhaps gas lamps with rellectors, on the ribs of the dome would answer 

 Die purpose. 



