44 REPORT 1871. 



seventeen meteors were observed, six in the first, six in the' second, and 

 five in the third hour of the watch. On the night of the 17th the sky was 

 again clear ; but three meteors only were observed in three-quarters of an 

 hour, between 10'' 55" and ll*" 40" p.m. The meteors observed on both 

 nights were small, and appeared generally with short courses near a radiant- 

 region around tt Herculis, from which they appeared to diverge. The num- 

 ber of meteors seen of the different magnitudes were, 2 = 1st mag.*, 4=2nd, 

 4= 3rd, 6= 4th, 4 = 5th : total 20 meteors seen in 3| hours by one observer, 

 in a clear sky, with no moon. 



V. Papers relating to Meteoric AsTROifOMT. 



1. Under the title * Alcuni Resiiltati Preliminari tratti dalle osservazioni 

 di SteUe Cadcnti publicate neUe Effemeride degli anni 1868, 1869, 1870;' 

 Professor Schiaparelli communicates, in connexion with the three Catalogues 

 of Shooting-Stars observed in Italy, published in the Ephemeris of the Milan 

 Observatory for the years 1868, 1869, and 1870, a first report on the radiant- 

 points obtained by mapping the meteor-tracks contained in them from Janu- 

 ary to June. For a convenient nomenclature of the radiant-points, the year 

 is divided into seventy-two pentads, of five days each, of which six are con- 

 tained in every month. While the first five pentads in every month are 

 complete, the sixth, and last, consists of three, four, five, or six days, ac- 

 cording to the length of the month to which it belongs. Since, however, the 

 observations for a single night of the year only (collected from all the years) 

 are combined together to detect the radiant-points, of which several may 

 occur in each pentad, the letters of the alphabet added to the Roman num- 

 ber of a pentad (thus, XIX. a) designate the radiant-points in those pentads in 

 the order in which they were successively discovered by Professor Schia- 

 parelli. Besides a strict separation of meteors observed on one from those 

 observed on the next following or on the next preceding night, to avoid the 

 risk of confusing together meteors belonging to different radiant-points under 

 a false assemblage of two radiant-points into a single meteoric-shower. Pro- 

 fessor Schiaparelli distinguishes as different meteor-currents those whose 

 radiant-points, as shown by laying down the recorded paths, are more than 

 10° apart. The precision with which the radiant-points must be determined 

 (from the shooting-star observations of a sinr/le night) is necessarily very 

 great, in order that this rule may be rigorously appUed. Even omitting the 

 errors of observation (which are frequently considerable), it is found that 

 different meteoric showers present different characters of radiation. In some 

 the radiant-region is small, and the meteor-tracks prolonged backwards meet 

 nearly in a point, when it is caUed " exact "; in others it is larger, the meteor- 

 tracks prolonged backwards crossing each other in a confused manner over a 

 considerable apparent space, in which case it is called " diffuse." The 

 shooting -stars which make their appearance witliin the radiant-region (when 

 this is rather large) may appear to be moving in every variety of opposite direc- 

 tions, and their paths are usually noticed to be extremely foreshortened by 

 perspective in this position. Lastly, if they diverge from two or more points 

 the character of the radiation is said to be double or multiple ; and it ap- 

 pears probable, on certain theoretical grounds, which will be shortly stated, 

 that a diffuse radiant-region in general arises from the close assemblage of 

 many radiant-points togetherinto a multiple group. The November meteor- 

 shower is an example of exact, and the August star-shower an instance 

 either of multii^le or of diffuse radiation, according to the various descriptions 

 of the observers who have examined the direction of its radiant-point most 



