146 KECORD OF SCIENCE FOR 1887 AND 1888. 



(14) The object-glasses shall be constructed in such a manner that 

 the field to be measured. shall extend at least 1 degree from the center. 



(15) In order to eliminate fictitious stars and to avoid inconvenience 

 from minute specks which may exist upon the plates, two series of 

 negatives shall be made for the whole sky. 



(16) The two series of negatives shall be so made that the image of 

 a star situated in che corner of a plate of the first series shall be found 

 as nearly as possible in the center of a plate of the second series. 



(17) Besides the two negatives giving the stars down to the four- 

 teentli magnitude another series shall be made with shorter exposures, 

 to assure a greater precision in the micrometrical measurement of the 

 fundamental stars, and render possible the construction of a catalogue. 



(18) The supplementary negatives, destined for the construction of the 

 catalogue, shall contain all the stars down to the eleventh magnitude 

 approximately. The executive committee shall determine the steps to 

 be taken to insure the fulfillment of this condition. 



(ID) Each photographic plate to be used in the formation of the cata- 

 logue shall be accompanied by all the data necessary to obtain the 

 orientation and the value of its scale ; and, as far as possible, these data 

 shall be written on the plate itself. Each i)late of this kind shall show 

 a well-centered copy of a system of cross-wires for the purpose of elimi- 

 nating errors which may be produced by a subsequent deformation of 

 the photographic film. Further details of this nature shall be deter- 

 mined by the executive committee. 



(20) In the negatives intended for the map the number of cross-wires 

 to be used in their control and reduction shall be reduced to a mini- 

 mum. 



(21) The tubes of the photographic instruments shall be constructed 

 of the metal most likely to give an invariable focal plane and shall carry 

 a graduation for the determination and regulation of the position of the 

 plate. 



(22) The executive committee shall choose the reference stars to be 

 used. 



(23) The question of the methods of measurement and the conversion 

 of the numbers obtained into right ascensions and declinations for the 

 equinox of 1900 is left to the executive committee. That committee 

 shall first occupy itself with the study and methods of use of measuring- 

 instruments, giving either rectangular or polar coordinates, and based 

 upon the simultaneous use of scales for the larger distahces, and mi- 

 crometer screws for scale subdivisions. 



(24) The connection of the plates will be effected in conformity with 

 resolution No. 16. 



At the last general session, April 25, the Congress delegated its pow- 

 ers to a permanent committee, consisting of the directors of the observa- 

 tories actually taking part in the work, and the following eleven mem- 

 bers chosen by ballot, viz. : Christie, Duner, Gill, Prosper Henry, Janssen, 

 Loewy, Pickering, Struve, Tacchini, Yogel, and Weiss. The observa- 

 tories of Algiers, Bordeaux, Cape of Good Hope, Greenwich, La Plata, 

 Melbourne, Oxford, Paris, Potsdam, Rio de Janeiro, Santiago, San Fer- 

 nando, Sydney, Tacubaya, Toulouse, have been pledged to co-operate, 

 and the instruments for several of them are well advanced. No observa- 

 tory in the United States has thus far signified definitely its intention of 

 co-operating, though the Government has been appealed to to appropri- 



