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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[October' 



the new observatory of Geneva takes a part successfully in the pro- 

 gress of science. Denmark possesses at Altona a model astronomical 

 observatory. Bavaria ciin equally pride itself on the establishment 

 founded near Munich, and Hanover on that of Gottingen. The obser- 

 vatory of Hamburgh is also worthy of remark. In Prussia the courses 

 of the stars are studied, under the auspices of the government, at 

 Berlin, Bonn, Breslau, and in particular ;it Konigsberg. The instru- 

 ments are excellent, and the buildings constructed on purpose, in com- 

 pliance with the minute requisitions of modern scii-nce. hi fliis gene- 

 ral career of enuilation, by which the most magnificent of sciences 

 everywhere profits, Russia has placed herself in the foremost rank. 

 Not satisfied with having very useful observatories at Durpaf, Abo, 

 Kieff, Kazan, and Nicolaieflf, on the Black Sea, she has just caused to 

 be built a true monument on the to|) of the Pulkova hill, near St. 

 Petersburg. This splendid central observatory of Russia has cost 

 more than two millions of rubles (£200,000), and among its finest in- 

 struments is to be observed a telescope bought at Munich for 80,000 

 rubles (£8,000). 



If discontented dispositions believe that such a great number of 

 observatories is useless, we would undeceive them by observing how 

 much more rapidly the field of science has been extended than the 

 means of investigation. We would, for instance, observe that looking 

 at first only to the stars perpetually visible, more than 150,000 stars, 

 formerly wrongly called fixed stars, are displaced each year, in pro- 

 portions of which it is incessantly necessary to determine the exact 

 value ; and that milliards of stars, hitherto neglected on account of 

 their excessive sraallness, now attract the attention of astronomers, 

 and seem intended to unveil the mysterious wonders of the firmament, 

 and that as to comets, of such short appearance that they must be ob- 

 served of a sudden, it has been necessary to provide against the long 

 cloudv atmospheres, which in Europe, sometimes render observation 

 impossible at a given spot for some weeks. Besides, was it not 

 natural that, in the nineteenth century, every nation should have the 

 noble ambition of taking part in astronomical discoveries, those of 

 which mankind should be the most justly i)roud, on account of their 

 certainty, magnificence and utility. In France, moreover, in this 

 respect we are far from prodigality; set aside the observatory of 

 Marseilles, often paralysed by the bad state of the building, and the 

 observatory, nearly finished, which the municipal corporation of Tou- 

 louse have just erected with such rare intelligence and such greiit 

 liberality, aiid what have we got left? The establishment in the 

 capital, in favour of which the Minister of Public Works now asks a 

 special vote. 



Taken altogether the ardour which is exhibited in the present day,= 

 by those engaged in the improvement of achromatic telescopes and 

 large divided instruments of observation, has contributed more to the 

 progress of astronomy than the exertions of all the governments in 

 Europe, in constructing new observatories and in modifying tlie form 

 and arrangements of the old ones. The first telescopes of the poor 

 optician of Middleburg, who invented those wonderful instruments, 

 had only a foot and a half focal distance. The telescopes with which 

 Galileo discovered the satellites of Jupiter and the phases of Venus 

 hardly magnified seven times. In none of the instruments of the im- 

 mortal Florentine did the linear niLignification exceed thirty-two 

 times. Huygens and Cassini possessed telescopes which magnified a 

 hundredfold, and they only reached this proportion by extending the 

 focal distance to 8 yards. A little later an object glass was brought out 

 by Auzout which magnified 600 times, but had 300 feet focal distance ; 

 and, as we have already said, notwithstanding a thousand clever con- 

 trivances, the management of a telescope in length equal to the height 

 of the spire of the Invalides would present insurmountable difSculties. 

 The opticians discouraged directed their whole attention, in imitation 

 of Newton, to reflecting telescopes. Very good instruments of this 

 kind were executed, but of very restricted size. In 1758, JohnDollond, 

 the son of a French refugee weaver, executed in England what New- 

 ton had declared to be impossible, namely, telescopes depriving the 

 images of stars of the rainbow borders which all simple objects en- 

 gender. Achromatic telescopes of small dimensions were found to 

 magnify as much as the 200 or 300 feet object glasses of Dampani, 

 Borelli andAuzout, and attention was then exclusively turned to them. 

 The English, whose manufacturers could alone produce flint glass 

 without streaks or striae, became possessed of the supply of achromatic 

 telescopes for the whole world. The skill of our neighbours, how- 

 ever, in the manufacture of glass was not such as to produce for the use 

 of opticians pure discs of flint and crown glass more than G inches 

 diameter. The images produced by a six-inch glass not having in- 

 tensity enough to magnify the planets so much as the wants of science 

 required, recourse was again had to reflecting telescopes. It was 



^ And la £iigl!ui<t fgr « very l«ne tliae.-^Trsiialator, 



then that the colossal instruments were produced, at the expense of 

 the King of England, which have immortalized Herschel. Achromatic 

 telescopes were necessarily again in vogue when the Svfiss workman 

 in a glass work near Munich succeeded in making flint glass without 

 streaks. Stimulated by the skill with which Fraunhofer turned the 

 glass to account, the English government endeavoured but in vain, to 

 recover possession of a branch of trade which it had allowed to be 

 carried off. The most powerful telescopes now used, even in the 

 English observatories, are made in the shops of Paris and Munich. 



The largest achromatic telescope known has only 11 inches aper- 

 ture. The effect of such an instrument it seems might be equalled 

 and even surpassed, within accessible sizes, by reflecting telescopes. 

 Lord Rosse, a wealthy peer in Ireland, is therefore now expending, 

 with infinite ardour and remarkable perspicuity, enormous sums in 

 experiments on the construction of telescopes of unused dimensions. 

 Things had reached this point when Messrs. Gumaud and Bontemps 

 presented to the Academy of Sciences masses of crown and flint glass 

 19 inches diameter, which seemed free from bubbles and streaks, and 

 these artisans engage to supply such masses even a yard wide. On 

 the other hand, opticians generously place at the disposal of learned 

 societies the mechanical means which they possess of modelling, 

 softening, and polishing these gigantic lenses. The most eminent 

 workman in our country also has promised to direct the undertaking. 

 In a brief space of time, if the Chamber carries the motion of the 

 Minister of Public Works, French astronomers will possess reflecting 

 telescopes superior to anything which yet exists, superior indeed to 

 anything that the most ardent imagination could last year have dared 

 to hope. In the meanwhile, the parallactic stand and the turning roof 

 of the east tower will allow us to turn to account several telescopes 

 which the difficulty of managing now leaves unused. 



Will the discoveries which great instruments presage be brilliant 

 enough to justify so much trouble and such great expense ? If we 

 quote a few facts, the Chamber will be able to reply for itself. Till 

 of late years we had not succeeded in determining the real distance 

 of a single star. All that astronomers knew was a limit within which 

 none of these stars could be situated. Now, by means of observations, 

 which will become easy with the large telescopes which the Board of 

 Longitude hopes soon to possess, tlie true distance of one star is known. 

 The small star called the (Jlst of Cygnus is so distant from the earth 

 that its light takes ten years to reach us. This star, therefore, if sud- 

 denly annihilated would be seen ten years after the catastrophe. It 

 must be remembered that light runs at the rate of 200,000 miles per 

 second, that the number of seconds contained in a day is 85,400, that 

 tlie year contains 3G5 days and a quarter, that the product of these 

 three numbers is to be multiplied by ten to ascertain in miles the in- 

 terval which separates us in a straight line from the Gist of Cygnus, 

 and it will be natural that astronomers should pride themselves on such 

 a result, and that they should desire to apply to other stars their mag- 

 nificent operations of surveying. Large telescopes with parallactic 

 fittings and of high magnifying powers will enable us to perfect our 

 observations on the fixed stars. The fact is now established that the 

 stars of almost all the binary groups are dependent on each other, 

 forming systems of suns, generally coloured, revolving around their 

 common centre of gravity. The exact measure of these movements 

 of rotation, combined with the determination of the real distance of 

 the two grouped stars, would mathematically conduce to a knowledge 

 of the sum of the two masses. When by a series of irrefragable de- 

 ductions mathematicians and astronomers succeeded in finding that 

 the mass of the sun is equal to 355,000 times tliat of the earth, or, in 

 other terms, when they recognized that the radiant star, placed in the 

 scale of an immense balance, would require for its equilibrium in the 

 opposite scale 355,000 globes such as the one we inhabit, the world was 

 struck dumb with astonishment. We can assert that still more will yet 

 be done. Men determined formerly the mass of a star which shows it- 

 self as an immense globe, a star around which the earth revolves, a star 

 which governs by its attractions, that is to say by an action dependent 

 on its mass, all the planetary movements. Every one, « priori, could 

 have vaguely foreseen some connection which might lead to the de- 

 sired result. Now, the question is to calculate the masses of certain 

 suns, suns belonging to other systems, suns placed at distances which 

 confound the imagination, suns which under the telescope present no 

 appreciable diameter, suns which the mere thickness of a spider's 

 web will conceal from the sight of an observer — here the strength of 

 science will be shown in all its majesty. The astronomer provided 

 with a telescope of large opening and high magnifying power, mounted 

 parallactically, and delicately governed by a clock, wilistill find afield 

 of research, almost untouched, in the vast and varied nebulosities with 

 which the heavens are sown. He will study the progress of concen- 

 tration in the phosphorescent matter; he will mark the period of 

 ounding in the external contour; the period of the appearance 



