INDUSTRIAL PROGRESS DURING THE YEAR 1874. X xix 



work on Donati's comet ; the spectroscopic observations by 

 Rayet, Lockyer, Secchi, Huggins, and others, and the polari- 

 scopic observations of Wright, Zenker, and Secchi ; from all 

 of which it may be concluded that the nucleus was a glowing 

 solid or liquid, unless, as some think, it may have been rather 

 a condensed group of clashing meteorites. The tail was evi- 

 dently illuminated to a considerable extent by the solar rays ; 

 concerning its chemical constitution, nothing definite can be 

 concluded, since the evidence is quite conflicting as to the 

 existence therein of any true gas. The appearance of en- 

 velopes was recorded by Huggins and Lockyer, the latter of 

 whom observed, with the great telescope of Mr. Newall, four 

 faint envelopes successively rising from the nucleus. Weber 

 searched for, but found no satisfactory proof of the rotation 

 of either tail or nucleus about an axis. 



In 1861 the spectroscope was in its infancy, and had not 

 been generally applied to celestial objects. It does not seem 

 that any one thought of examining the great comet of that year 

 with such an instrument. The comet of 1874 is therefore of 

 great interest as the first brig-ht one to be observed with the 

 spectroscope. Unfortunately its position during the period 

 when it was brightest was quite unfavorable, being so near 

 the sun that it could be seen only when very near the hori- 

 zon. For this reason perhaps the result was disappointing, 

 nothing remarkable being discovered in the spectrum. The 

 latter was found to comprise, first, a faint continuous spec- 

 trum, probably produced by reflected sunlight, and, second, 

 three brio-ht bands. The latter have been seen in all com- 

 ets hitherto examined with the spectroscope, and therefore 

 form no new feature. They have always been found to coin- 

 cide with the spectrum of carbon, and, from this circumstance, 

 the theory that comets consist of some sort of carbonic va- 

 por may be considered as strengthened by the observations 

 in question. 



Meteoroids. Shooting-stars form the subject of a valuable 

 report to the British Association by Mr. Glaisher and Mr. 

 Gregg, the latter of whom has computed a number of cases 

 in which there is an agreement between the orbits of meteors 

 and comets. At the Toulouse Observatory an extraordinary 

 passage of corpuscles across the sun's disk was observed on 

 the 5th, 6th, and 7th of September. 



2* 



