August 24, ISS?.] 



SCIENCE. 



•J3:i 



siileration of it, and tlie preparation for it, to his 

 zealous frionds In the council. 



Upon the motion of Struve, the society by a rising 

 vote, expressed its oontideiiee in the assurance of tlie 

 president that he would bring forward his plan at tlie 

 proper time, as soon as the means for its execution 

 could Ix; assured. 



At the meeting held at Bonn in 1S07, Argelander 

 again brought up the subject in a communication 

 which appears to have been an exhaustive discussion 

 of the whole problem. This paper is not printed in 

 the proceedings of the ge-^ellschaft; but at its con- 

 clusion a committee was appointed to take definite 

 action with respect to the recommendations which it 

 contained. The committee reported at the same 

 session; and their report, which is published in the 

 place of the paper pre>ciiti'il by Argelander, is prob- 

 ably identical in substance with it. The plan pro- 

 posed and adopted was finally published in the form 

 of a programme, in which the details of the work 

 are arranged with considerable minuteness. As this 

 programme has been widely di-tributed, it .'■eenis 

 unnecessary to give any thing more than a general 

 abstract of it. Since it differs in a few minor points 

 from the first report of the cominiltee at the Bonn 

 meeting, the essential features of this report will be 

 given instead of an abstract of the programme itself. 



They are as follows: — 



a. The limits in declination of the proposed series 

 of observations are — 2° and -|- S0°. The first limit 

 was chosen on account of the lack of suitable funda- 

 mental stars south of the equator. It is probable, 

 also, that Argelander had a suspicion of the fact, 

 since proven, that the uncertainty with respect to 

 the systematic errors of southern stars is, of necessity, 

 considerably greater than for northern stars, and that 

 on this account it would be better to defer this part 

 of the work until further investigations in this direc- 

 tion could be made. 



The limit + 80° was chosen because the repetition 

 of Carrington's observations between 81° and flO° 

 was considered superfluous, and Hamburg had already 

 undertaken the extension of Carrington's observa- 

 tions from 81° to 80°. 



h. Within these linuts, all stars in theDurchmus- 

 terung to the ninth magnitude, and, in addition, all 

 stars which have been more exactly observed by La- 

 lairde, by Bessel at Koeiugsberg, and by Argelander 

 at Bonn, are to be observed. 



c. The observations are to be differential. The 

 clock errors are not to be found from the fundamen- 

 tal stars usually chosen for this purpose, and the 

 equator point corrections are not to be derived from 

 observations at upper ami lower culminations, but 

 these elements are to be derived from a series of 500 

 or 600 stars, distributed as uniformly as possible over 

 the northern heavens. The exact co-ordinates of 

 these stars are to be determined at Pulkova,. thus 

 securing the unity necessary in order to connect in 

 one system the observations of different zones. 



d. Every star is to be observed twice. If the two 

 observations differ by a quantity greater than ought 

 to be expected, a third observation will be necessary. 



e. In order to facilitate the work. It will be desira- 

 ble to use only three or four transit threads, and only 

 one or two microscopes. In order to facilitate the 

 reductions to apparent place, the working-list of stars 

 should be comprised within narrow limits. 



/. Before the commencement and after the close 

 of each zone, two or three fundamental stars are to 

 be observed upon the same threads and w ith the same 

 microscopes as were used in the zone observations. 

 When the seeing is not good, and when for any other 

 cause it seems desirable, one or more fundamental 

 stars may be observed in the course of the zone. 

 The number and selection of the stars will depend 

 upon the character of the instrument employed. It 

 it remains steady for several hours, and has no 

 strongly marked flexure or division errors, or if these 

 errors have been sharply determined, the fundamental 

 stars may be situated ten degrees or fifteen degrees 

 away from the zone limits. However, there must 

 remain many things for which no general rule can 

 be given, and which must be left to the judgment of 

 the observer, aided by an accurate knowledge of his 

 instrument. 



3. With a RepsoM or a Martin instrument, one 

 microscope will be suflScient, if its position with re- 

 spect to the whole four can be determined. It will 

 be suflSeient, if the change in position during the 

 observations can be interpolateJ to 0.2". 



A. It will be desirable to divide beforehand the 

 zones into such time intervals that the observations 

 can be easily made. 



i. Zones exceeding one and one-half or at the most 

 two hours are not advisable, first, because the zero 

 points will be too far apart, and, second, because a 

 longer duration will involve too much fatigue physi- 

 cally and mentally. 



At the conclusion of this report, all the astron- 

 omers present who were willing to take part in this 

 work were requested to communicate with the coun- 

 cil, stating the region of the heavens which they pre- 

 ferred to select for observation. 



At this meeting, Berlin, Bonn, Helsingfors, Leip- 

 zig, and Mannheim signified their intention to share 

 in the work. Leiden also expressed its intention of 

 taking part as soon as the work already undertaken 

 should be completed. 



When the stars to be observed had been selected 

 from the Durchmusterung, it was found that the 

 number would not vary much from 100,000, requiring 

 rather more than 200,000 observations. I'reparatious 

 for the work of observation were immediately com- 

 menced ; and, by the time of the next report in 1809, 

 considerable progress had been made. 



In the report for this year, the provisional places of 

 a catalogue of .5.19 fumlamiintal stars were jiublished. 

 This catalogue is composed of two parts. The list 

 of hauptsterne consists of 3:!6 stars to the fourth 

 magnitude, observed at Pulkova by Wagner with 

 the large transit instrument, and by Gylddn with the 

 Krtel vertical circle. The list of zusat-sterne consists 

 of 20.3 stars fainter than the fourth magnitude. As 

 the details of the work in the formation of the pro- 

 visional places of the stars of this list are not given 



