142 REPORT — 1866. 



on the night of the 10th was for the most part cloudy, and all attempts to 

 catch the spectrum of a meteor pi'oved in vain. 



Spectrum observations were begiln at Hawkhurst on the evening of the 9th ; 

 and the sky proving remarkably clear for this kind of observations, they were 

 continued, imtil daybreak, on the following nights of the 9th and 10th. 



No difficulty was found in mapping the coiu'se of the meteors in the spec- 

 troscope by the stars, of which a whole constellation, as for example the seven 

 stars- of Ursa Major, are seen in the instrument at once. The brightness, 

 duration, and length of path, and whether the meteor left a streak upon its 

 course, could also be noted in the instrument as readily as with the unassisted 

 eye ; so that by this means the apparent paths of 17 meteors were noted in 

 six hours, of which all, or all but one, diverged from Perseus and Cassiopeia. 

 The proportions of magnitudes were as follows : — 



=Sirius. =l8tmag. =2nd mag. = 3rd mag. == 4th mag. 



2 4 4 4 2 



The spectroscope being so held that the cpurse of the meteors was parallel 

 to the refi'acting edges of the prisms, the appearance of their meteoric spectra 

 was found to be, in general, altogether different from the view of the same 

 meteors obtained by the naked eye. N'evertheless in one instance (No. 8) 

 the appearance of a meteor in the spectroscope was unaltered, being that of 

 an ordinary bright shooting-star, leaving a slender yellow streak upon its 

 course. In some cases (of the most conspicuous streaks), the appearance of 

 the brightest and last fading portion of the streaks in the spectroscope was 

 the same as to the naked eye, being a bright-yellow-coloured, slender line. 

 Lastly, when the spectrum of the meteoric streak was diflPiise, a bright-yellow 

 very slender line was frequently observed in the spectrum on the side towards 

 the red, which either faded away simultaneously with the diffiise portion of 

 the spectrum, or, more commonly, remained visible alone after that portion 

 of the spectrum had disappeared. The bright-yeUow line was observed in 

 eight cases among 1 7 meteoric spectra. Its presence in a very conspicuous 

 form in many of the streaks leads Mr. Herschel to the conclusion that the 

 metal sodium is abundant in the 10th of August meteors. The following 

 account of the original discovery of a yellow line strongly resembling that 

 of sodium in the train-spectra of the August meteors, is taken from Mr. 

 Herschel's description of the observations, in the ' Intellectual Observer ' 

 for October, 1866, where it is accompanied by a tinted plate : — 



" All the necessaiy preparations having been made, and with the prospect of 

 a considerable meteoric shower at hand, a watch for meteors was commenced, 

 in order to observe their spectra, on the night of the 9-lOth of August last. 

 Expectation on the first night was not destined to be disappointed, and six 

 meteors were observed to pass across the field of view. Notes of the peculia- 

 rities were made, and of the general appearance of their spectra, and are 

 briefly as follows : — 



" Auc/ust 9th. — No. 1, S'^ 40" p.m. About equal to a fourth-mag. star. 

 Passed across the body of Cygniis in half a second, leaving no streak. The 

 spectrum exactly resembled that of a fourth-mag. star (o Cygui), close to which 

 the meteor passed, the conclusion being that the meteor might be a solid body 

 heated to ignition. 



" August 10th. — No. 2, 0'' 27" a.m. Nearly as bright as Sirius. Com- 

 menced near Polaris (in the field of view), and shot 15° or 20° (beyond the 

 field of view) along a line dii'ected from Cassiopeia, leaving a streak on its 

 whole course for four seconds. The latter part of the meteor's course was 



