398 REPORT — 1873. 



nected witli Biela's comet might pursue to make it probable that this tele- 

 scopic body is at least a member of the cometary group, of which it is not 

 impossible that the double comet of Biela may contain other representatives 

 hitherto not detected by telescopic observations*. Should the principal bodies of 

 Biela's comet have undergone no uncalculable perturbations, it is shown by 

 Mr. Hind (' Monthly Notices,' vol. xxxiii. p. 320) that up to its expected return 

 in the year 1866, no calculable causes depending upon its actual position until 

 that time have been overlooked, and that if uninvestigated disturbances may 

 yet explain its presence in the recent meteor-shower at a place of its orbit which 

 •it should have passed at least twelve weeks before the date of the meteor- 

 shower, those disturbances must have affected its course during the last re- 

 volution (1866-73) which the comet has performed. It appears more pro- 

 bable that the comet has faded out of sight ; and it is pointed out by Professor 

 Schiaparelli, in a new volume of three lectures on meteors pubUshed in con- 

 nexion with these recent discoveries at Florence, that more than one instance 

 of variability has been observed in comets, of which the two portions of 

 Biela's comet itself presented a remarkable example at the last return, when 

 interchanges of brightness were observed between them. It may also be 

 added that when first discovered to be periodical in the year 1826, it was 

 found to be identical with a comet observed in the years 1772 and 1805, 

 having accordingly escaped observation during two previous series of returns 

 in this and the last century, when it might be expected to have been detected^ 

 had not some diminution of its light, perhaps, rendered it invisible on each of 

 those occasions. Telescopic and meteoric observations may thus be found, if 

 perseveringly conducted and comprehensively carried on together, to assist 

 each other in tracing the effects of the sudden variations in their physical 

 condition to which comets, from their small masses and highly eccentric 

 orbits, are exposed, more than all other classes of astronomical bodies, in 

 their circumsolar revolutions. 



The newly discovered connexion between meteor-showers and comets, 

 according to which the periodic comet of Biela and the recently observed 

 star-shower are associated members of a common stream of bodies following 

 each other in nearly the same path about the sun ; and the question of the pro- 

 bable nature of the physical connexion between the invisible particles of the 

 meteor-stream, and the faintly or brightly luminous body of its attendant 

 comet, have given rise to considerable discussion respecting the extent and 

 mode of the connexion in which comets in general, and all the different 

 forms of meteoric substances may possibly be regarded as allied phenomena. 

 "With respect to appearances of the latter class, it must be admitted that 

 many of the grounds for such conclusions regarding detonating fireballs and 

 aerolites are hitherto verj^ indefinite and uncertain. The directions and real 

 velocities in space of very few aerolites and detonating meteors have been 

 exactly ascertained ; while, on the other hand, the collected proofs derived 

 from observations of a distinct connexion between star-showers and periodic 

 comets are as abundant and precise as the most rigorous process of research 

 in any kindi-ed subject of scientific inquiry would demand. Eeviewing 

 certain instances of hyperbolic velocities of fireballs and aeroli tes that have 

 been sufficiently well observed to be accepted as examples of their class, and 

 contrasting the evidence which they present with the remarkable absence 

 among comets of very excentric hy]Derbolic orbits. Prof. Schiaparelli is led to 

 recognize two different original sources of these two classes of bodies, and to 

 regard comets as cosmical bodies belonging to the same star family, or " star- 

 * Astronomical Society's ' Montlily Notices,' vol. xxxiii. pp 128 & 130. 



