»1MJ6 Royal Astronomical Society. 



the assurance of number of observations, and consequent power of 

 detection, to the data on which future planetary tables will be con- 

 structed, each one has tried, or is trying, to make the greatest pro- 

 gress of some one branch of astronomy peculiarly its own work. Thus, 

 while Greenwich has constantly devoted its peculiar attention, pur- 

 suant to the will of its founder, to the moon, the large equatoreal at 

 Cambridge has suggested the researches of the Plumian Professor ; 

 the Radcliife observer at Oxford has devoted his special attention to 

 the circumpolar stars, and will soon be furnished with a new mode of 

 action by the possession of the splendid heliometer which is in prepa- 

 ration ; and our lamented colleague at Edinburgh has left the materials 

 for a catalogue of zodiacal stars. Differences of locality, of instru- 

 ments, of mode of government, of taste and reading in the directors 

 of different observatories, will originate differences of plan ; it may 

 be permitted to a body so closely connected with the common pursuit 

 as your Council, and so deeply interested in the astronomical welfare 

 of each and all of these institutions, to hope that these differences of 

 plan will one day arise out of a matured system of co-operation, in 

 which foreign observatories will be combined with our own. Much 

 advantage has arisen in this country from the division of labour, 

 which has thrown the observation of double stars and nebulae upon 

 the amateur astronomer ; and more will always be gained, the larger 

 the amount of strength and the wider the range of researches which 

 are thus judiciously subdivided. 



The benefit of co-operation has been lately seen in the junction 

 of the observatories of Pulkowa, Altona, and Greenwich, for the de- 

 termination of their differences of longitude. Our associate, M. 

 Struve, had connected Pulkowa and Altona ; and, having strongly 

 represented to his government the propriety of taking Greenwich as 

 the zero point for all longitudes, it was resolved to connect the two 

 last-named observatories. A portable transit was erected during 

 the last summer in a temporary observatory on tlie grounds of the 

 Royal Observatory, and forty-two box chronometers were carried 

 backwards and forwards by the steam-boats, eight times each way. 

 At first M. Otto Struve observed at Greenwich, and M. Dollen at 

 Altona, for two voyages : the observers M'ere then reversed for four 

 voyages, and again resumed their old stations for two more ; by 

 which arrangement it was hoped to eliminate both personal equation 

 and its gradual changes. The clock in the temporary observatory 

 w^as regularly compared with the Greenwich transit clock, so that 

 tlie ordinary observations of the Observatory will contribute to the 

 result : to this end all necessary observations for personal equation 

 were made. The result is not yet completely calculated. 



While the preceding operation was in progress, another of a simi- 

 lar kind was undertaken by the Astronomer Royal and Mr. Sheep- 

 shanks, for the connexion of Valentia in Ireland (the western point 

 of Europe) and Greenwich ; to which was added, the incidental de- 

 termination of the longitude of Liverpool Observatory and Kingstown 

 Harbour. Valentia is nearly in the latitude of Greenwich, and it 

 will probably be the extremity of an arc of parallel extending across 



