86 



KNOWLEDGE 



[April 1, 1895. 



of the sodium molecules. I have already carefully con- 

 sidered this possibility, and, without going into details 

 which would be out of place in a letter, I may state that 

 experiments made specially to test this point have clearly 

 shown that such actions are not concerned in the radiation. 

 For a full discussion of all my experiments I would refer 

 M. Deslandres to my article on the radiation of gases, 

 which will shortly be published. 



With regard to Prof. Lockyer's experiment, referred to 

 by M. Deslandres, I must say I fail to see how this bears 

 on the question at all. By submitting sodium vapour to 

 the electric discharge, a new factor is introduced which 

 may well complicate matters. The curious result obtained 

 does not prove that hydrogen interacts with sodium in any 

 way ; but might be simply explained by supposing that the 

 discharge prefers to travel by means of the more lively 

 hydrogen molecules, which are thus set vibrating whilst 

 the sodium molecules remain unaffected. 



Yours truly, J. Evershed. 



THE OBSERVATORIES OF ONE HUNDRED 

 YEARS AGO. 



By W. T. Lynn, B.A., F.R.A.S. 



ON the 11th of June, 1795, Dr. (afterwards Sir 

 William) Herschel communicated to the Royal 

 Society a description of his forty-feet reflecting 

 telescope, the construction of which, he remarks, 

 was begun about the latter end of the year 1785 

 and finished at the end of August, 1789. It may be 

 interesting to run through the list of observatories which 

 were in operation at that time, as showing the marvellous 

 progress which has been effected in the means of astro- 

 nomical research during the hundred years which have 

 since elapsed. Expeditions were made to observe special 

 phenomena, such as transits of Venus, in the southern 

 hemisphere, Halley had made a series of observations at 

 St. Helena and Lacaille at the Cape of Good Hope, but 

 no permanent observatory existed in that hemisphere. 

 Nor did the whole of the American continent contain 

 one ; so our survey is practically confined to Europe. An 

 observatory, it is true, had been built at Peking more than 

 five hundred years before the last century, and observations 

 were made in it by Verbiest and the .Jesuit missionaries 

 for about a century after 1673, but its activity had ceased 

 before the time of which we are speaking. 



The Greenwich Observatory, in 1795, had been for about 

 thirty years under the superintendence of Dr. Maskelyne, 

 and continued so for about sixteen years more. The value 

 of his observations (the first which were made at Greenwich 

 with achromatic telescopes) can never be over-estimatod, 

 although this is not the place to enlarge upon them. But 

 at the present time, whilst Eucke's comet is with us again, 

 it may be of interest to note that he observed this comet 

 in the year of which we are speaking, a few days after it 

 had been detected by Caroline Ilerschel and observed by her 

 brother. Mr. Denning has remarked on the fact that in all his 

 long career Sir W. Herschel never discovered a comet. 



The only other observatory which appears to have 

 existed at this time in England was the Radcliffe at Oxford. 

 This was founded in 1771 at the instance of Prof. Ilornsby, 

 and observations were made from-^i'^ ;/-g ^{ ;^^ com.'^le- 

 tion, but were not publishg^ regularly until the commence- 

 ment of Johnson s. :ppointment in 1839. They have been 

 contmuous ^^,-j. gj^^g mj,Jer the energetic administration 

 °' janson and his successors Main and Stone. This 

 Country had, however, at the time, one or two amateur 

 observers, chief among whom was the Rev. F. Wollaston, 

 of Chislehurst. Two observatories were also in operation 



in Ireland in 1795 ; those of Dublin (or Dunsink) and 

 Armagh. The former was erected in 1785, the first 

 director being Prof, (afterwards Bishop) Brinkley. The 

 latter was founded by Archbishop Robinson in 1791, but 

 it cannot be said to have contributed much to the progress 

 of astronomy imtil it was enlarged and provided with 

 better instruments by Archbishop Beresford in 1827, soon 

 after the appointment of Dr. Robinson as director. 

 Scotland at that time possessed no observatory. 



The Paris Observatory (also called Royal at first) was 

 founded a few years before that of Greenwich, and the 

 discoveries of Cassini I. gilded its early years. One 

 hundred years ago France was still in its revohitionary 

 epoch, and scientific activity was necessarily to a great 

 extent in abeyance. The National Convention was at the 

 head of affairs during the greater part of 1795. CassLni, 

 the fourth and last director, was not only practically 

 ejected imder pretence of establishing a divided jurisdiction 

 or quasi- republican form of government at the observatory, 

 but afterwards thrown into prison. It was not until the 

 opening of the nineteenth century that Lalande took the 

 principal position at the now National Observatory, M^chain 

 succeeding to it in 1801, and Bouvard in 1811, when it 

 had become Imperial. 



In Germany, Berlin had had for ninety years a small 

 observatory, erected in 1705 as part of the building of the 

 Academy of Sciences, and this was not superseded until 

 the time of Encke, under whom the new observatory 

 was constructed and equipped, but not finally completed 

 until 1826. The Seeberg Observatory, from which Encke 

 removed to Berlin, was founded by Duke Ernest II. in 

 1791, and was the scene of the labours of Von Zach, 

 Lindenau, Encke, and Hansen, in whose time it was 

 removed to Gotha. Gottingen University possessed an 

 observatory even earlier, in which Tobias Mayer made his 

 observations ; this was superseded by the present building 

 in 1811. Leipzig also had a university observatory founded 

 in 1787 ; it was here that d'Arrest in later times made 

 his observations, and it was not superseded until 1861, 

 when the new observatory was erected under the 

 direction of Prof. Bruhns. At Lilienthal, near Bremen, 

 Schroter's private observatory was established in 1779, 

 and work was continued there until the year 1813. An 

 observatory, removed to Karlsruhe in 1879, was fotmded 

 at Mannheim in 1772. Not much, however, emanated 

 from it until 1860, when improved instruments were 

 obtained, and Schonfeld commenced his observations on 

 uebula\ Vienna possessed an observatory, forming part 

 of the university building, in 1756, but the position was 

 very unsuitable, and the equipment very insufficient, so 

 that but little astronomical work was done in the capital 

 of Austria until 1820, when the observatory was rebuilt 

 and better equipment provided. It was superseded by the 

 present splendid establishment at Wiihring, on the ridge to 

 the north-west of the city, which was commenced in 1874, 

 and finished in 1879. Prague has had a university 

 observatory since 1751, but very few astronomical obseri- 

 vatious were taken there, and at present the work is 

 almost confined to magnetic aud meteorological investiga- 

 tions. Budapest has a royal observatory, founded in 1777, 

 and a new building was erected in 1813, but scarcely any- 

 thing has emanated from it. Kremsmunster, in Upper 

 Austria, has possessed an observatory even longer. It was 

 gg^^^ablished at the gymnasium of the Benedictines in 1748, 

 but" instruments w-ere H9*' .Provided to make it of any 

 practical use until many years afterwa.''i?.^- 



Tarniug to Holland, one finds that both Leyden aSd 

 Utrecht possessed university observatories at the end of 

 the last century, but neither had provisions for making 



